Hibiscus syriacus, Hibiscus mutabilis, and Confederate rose are all members of the Hibiscus genus in the Malvaceae family and are trees frequently cultivated in horticulture for ornamental purposes. Their most distinctive feature is the large, beautiful red to white flowers they produce, but they can often be confused with each other. These can be clearly distinguished by first examining the leaf shapes of Hibiscus syriacus, Hibiscus mutabilis, and Confederate rose. While the differences between Hibiscus syriacus and Confederate rose are minor and at the cultivar level, they differ in how the flowers bloom and the color variations of the flowers. This article will explain the classification and morphology of Hibiscus syriacus and Hibiscus mutabilis.

What are Hibiscus syriacus, Hibiscus mutabilis, and Confederate rose?

Hibiscus syriacus, also known as rose of Sharon, is a deciduous shrub native to China and Korea, with records of its cultivation in Japan dating back to the Azuchi-Momoyama period. It is cultivated in gardens, parks, and along roadsides, and escaped plants can be found growing in fields and on riverbanks (Kanagawa Prefecture Flora Survey Association, 2018).

Hibiscus mutabilis, also known as the hibiscus flower, is native to central China and has been cultivated worldwide since ancient times, including in its native region. In Japan, it has naturalized in the Izu Peninsula, Kii Peninsula, southern Shikoku, southern Kyushu, and Okinawa (Mogi et al., 2000).

'Versicolor', also known as the 'Drunken Hibiscus ', is a horticultural variety of hibiscus.

All of these trees belong to the genus Hibiscus in the Malvaceae family and are frequently cultivated in horticulture for ornamental purposes. Their most distinctive feature is the large, beautiful red to white flowers they produce. In the case of single-flowered varieties, a structure called the "pillar," which is a fusion of stamens and pistils, extends from the center of the five-lobed corolla.

These characteristics may often lead to confusion.

What are the differences between Hibiscus syriacus, Hibiscus mutabilis, and Hibiscus mutabilis?

Of these three species, the rose of Sharon and the hibiscus and Confederate rose are completely different species, with the Confederate rose being a variety of the hibiscus (Kanagawa Prefecture Flora Survey Association, 2018; Hayashi, 2019).

Looking at the leaves is crucial to understanding the specific differences.

In the case of the rose of Sharon, the leaf blade is rhombo-ovate with a wedge-shaped base, whereas in the case of the hibiscus, the leaf blade is ovate with 3 to 7 angles and a heart-shaped base.

A more easily discernible difference is that the leaves of the rose of Sharon are hairless and glossy, while those of the hibiscus are hairy, rough, and lack gloss. This is immediately obvious.

The leaf stalks of the rose of Sharon are also shorter than those of the hibiscus.

Based on the above, it takes a little practice, but you can distinguish between the two types.

The difference between Hibiscus mutabilis and Hibiscus syriacus is at the variety level, so their basic structure is exactly the same.

However, while the common hibiscus has single flowers and its color is fixed between red and white, the sweet hibiscus has double, larger flowers that change color from white to pink.

The fact that the color changes depending on the time of day is difficult to notice just by looking at it, but if the flowers are pale in color and double-flowered, you should suspect they are Confederate Roses (Hibiscus mutabilis). The Japanese name "Suifuyou" (酔芙蕉) is said to come from the fact that the way the flower changes color makes it look like someone is drunk from drinking alcohol.

Incidentally, the double-flowered variety, whose color remains unchanged, is called Yaefuyou Hibiscus mutabilis 'Flore Pleno'.

While there are many cultivated varieties of hibiscus, thanks to extensive breeding efforts, we will omit the details of their differences here.

Are there any other similar species?

For information on the differences between this hibiscus and the Sakishima hibiscus, which is even more similar, please see our separate article.

What are the differences between Hibiscus mutabilis (Fuyou) and Hibiscus sakishimaensis? We explain how to distinguish between similar species! Do slight differences in flower shape affect pollination strategies?

Both Hibiscus mutabilis and Hibiscus sakishimaensis belong to the Hibiscus genus of the Malvaceae family. They produce large, beautiful flowers, and when naturalized, they both grow in disturbed locations, making them difficult to distinguish. The difference can be achieved by carefully observing the leaves and stellate hairs. There are also slight differences in flowering period and flower color. Flowers...

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Other members of the same Hibiscus genus are introduced in a separate article.

There are differences between hibiscus and Japanese hibiscus! What are the differences between Japanese hibiscus and wind chime hibiscus? Is their origin unknown? When did they arrive in Japan? Do birds visit wild flowers?

Hibiscus, also known as hibiscus rosa-sinensis or wind chime hibiscus, is a popular evergreen shrub in gardening, known for its vibrant red-based flowers that evoke a tropical atmosphere. Sometimes, hibiscus and wind chime are used interchangeably, but...

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References

Hayashi, Masayuki. 2019. Tree Leaves: Expanded and Revised Edition - Identifying 1300 Species Through Real-Life Scans. Yama-kei Publishers, Tokyo. 824pp. ISBN: 9784635070447

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Mogi, Toru; Ota, Kazuo; Katsuyama, Teruo; Takahashi, Hideo; Shirokawa, Shiro; Yoshiyama, Hiroshi; Ishii, Hidemi; Sakio, Hitoshi; and Nakagawa, Shigetoshi. 2000. Flowers Blooming on Trees: Polypetalous Flowers (Vol. 2, 2nd edition). Yama-kei Publishers, Tokyo. 719pp. ISBN: 9784635070041

Styrax japonica, Pink Chime, and Styrax obassia all belong to the Styrax genus of the Styracaceae family and are familiar plants often found in gardens. Morphologically, a characteristic feature is that the flower stalks grow downwards towards the ground, and the flowers bloom facing downwards. However, some people may not know how to distinguish between them. Pink Chime is a horticultural variety of Styrax japonica, and the only difference is that the flowers are pink. Styrax japonica and Styrax obassia are completely different species and can be distinguished by the shape of their leaves and how their flowers are arranged. In addition, plants such as Chishanoki, Deutzia, Symplocos chinensis, and Stewartia pseudocamellia are often searched along with Styrax japonica, but Chishanoki is simply a name confusion, and Deutzia, Symplocos chinensis, and Stewartia pseudocamellia only have slightly similar flower colors and are not easily mistaken for each other if you look closely. This article will explain the classification of the Styrax genus.

What are Styrax japonica, Pink Chime, and Styrax obassia?

Styrax japonicus, also known as the Japanese snowbell tree (Egonoki or wild jasmine), is also called Rokurogi, Chishanoki, or Yamachis. It is a deciduous small tree distributed in Hokkaido (eastern), Honshu, Shikoku, Kyushu, the Ryukyu Islands, Korea, and China, growing in mixed forests at the foot of mountains, in mountain valleys, and along streams (Kanagawa Prefecture Flora Survey Association, 2018). Although its scientific name is written as Styrax japonica in various media such as the Japanese Wikipedia, according to Ylist, this is an old scientific name (synonym). Styrax japonicus is used worldwide (RBG Kew, 2023).

Styrax japonicus 'Pink Chimes', also known as Pink Chimes, Red-flowered Styrax, or Beni-ego, is a cultivated variety of Styrax japonicus grown in Japan and does not grow wild.

Styrax obassia, also known as white cloud tree, is also called large-leaved lettuce. It is distributed in Hokkaido, Honshu, Shikoku, Kyushu, Korea, and China, and is a deciduous small tree or tree that grows in hills and mountainous areas.

All of these plants belong to the genus Styrax in the family Styracaceae, and are familiar plants that are often cultivated in gardens and other horticultural purposes.

Morphologically, the main common features are that the flower stalks extend downwards towards the ground, the white flowers usually bloom facing downwards, and the corolla lobes are arranged in a tile-like pattern. Another common feature is the presence of stellate hairs on the underside of the leaves.

However, some people may not know how to distinguish between them.

What are the differences between Styrax japonica, Pink Chime, and Styrax obassia?

First and foremost, Pink Chime is simply a cultivated variety of Styrax japonica, so there are no fundamental structural differences between Styrax japonica and Pink Chime. However, it is significantly different from another species, Styrax obassia.

Specifically, the differences are that in Styrax japonica and Pink Chime, the leaves are somewhat rhombic-ovate (rarely lanceolate) and small, and the flowers are only 1 to 4 at the end of long pedicels, while in Styrax obassia, the leaves are round and large, often with fangs at the tip, and the flowers are numerous with short pedicels forming a raceme.

A peduncle (or stem) is the thin part that connects the flower to the plant body.

Another difference between wild Styrax japonica and Styrax obassia is that Styrax japonica grows from lowlands to mountainous areas, while Styrax obassia usually grows in mountainous areas.

The difference between Styrax japonica and Pink Chime is slight: Styrax japonica has white flowers, while Pink Chime has pink flowers. Pink Chime does not grow wild.

In addition, there is another species called Styrax shiraiana, which is distributed in the Kanto region (including Tochigi Prefecture), Shikoku, and Kyushu, and is very similar to Styrax obassia. However, its leaves are smaller, around 7 cm in diameter compared to Styrax obassia's 15 cm, and usually have large serrations, so they are not perfectly round (Hayashi, 2019). Furthermore, it has fewer stellate hairs on the underside of the leaves, the inflorescence is shorter, the flowers are smaller, and the tree height is somewhat lower, around 3 to 7 m.

There is also a variety of Styrax japonicus f. pendulus, which has drooping branches and leaves. It is sometimes used in bonsai.

The variety Styrax japonicus var. kotoensis, also known as red-headed styrax, is distributed in Kyushu (south of the Tokara Islands) to Okinawa in Japan, as well as in Taiwan and the Philippines. It was previously thought to be distinguishable from Styrax japonica by its slightly larger flowers and fruits, less prominent leaf serrations, and much earlier flowering period (autumn to spring). However, recent research has concluded that it is indistinguishable from Styrax japonica and treats them as the same species (Ohashi et al., 2017).

What is the difference between Styrax japonica and Styrax japonica?

The difference between Styrax japonica and Lettuce (Styrax japonica) is also a frequently searched topic.

The name "Chishanoki" (meaning "lettuce tree") has two confusing meanings.

First, let's look at another name for the Styrax japonica tree. In this case, we can say that "Styrax japonica = Chishanoki." In the Kabuki play "Kyara Sendai Hagi," a plant called Chishanoki appears, and this plant is actually Styrax japonica.

However, secondly, from a biological and taxonomic perspective, "chishanoki" usually refers to a plant belonging to the Boraginaceae family. This plant is also known as "kakinokidamashi" and its scientific name is Ehretia acuminata var. obovata.

As can be seen from its classification, this Styrax japonica is a completely different species from Styrax japonica, and they have almost no common features. If anything, the only similarity is that both have white flowers, but Styrax japonica clearly has smaller flowers, more flowers per inflorescence, and a larger corolla.

Furthermore, while the leaves of the Japanese snowbell tree (Styrax japonica) have serrated edges, those of the Japanese laurel (Chisha kiusiana) have entire margins without serrations.

This raises the question of why the Styrax japonica and the Chishanoki tree share the same name, but to put it simply, it seems to be a coincidence.

The alternative name for Styrax japonica, Chishanoki, is derived from the Japanese dialect name "Chinai" in the Chugoku region. Chinai is said to mean Chinari (meaning "milk-bearing"), referring to the appearance of the tree bearing abundant fruit, and it is believed that Chinari was corrupted into Chishanoki (Fukatsu and Kobayashi, 1993).

On the other hand, the name of the Boraginaceae tree, *Lactuca sativa*, is said to derive from the fact that the taste of its young leaves is similar to that of lettuce (*Lactuca sativa *).

Based on the above, let's make sure not to confuse them.

What are the differences between Styrax japonica, Deutzia crenata, Symplocos chinensis, and Stewartia pseudocamellia?

It seems that people often search for the differences between Styrax japonica, Deutzia crenata, Symplocos chinensis, and Stewartia pseudocamellia along with Styrax japonica. This is probably because their white flowers look somewhat similar.

However, if you look closely, you'll quickly notice the difference.

Stewartia monadelpha, also known as Japanese stewartia, belongs to the Camellia family. Its most distinctive feature is that its stamens are significantly more numerous and larger than those of other species, and the filaments fuse together in the middle to form a tube. This feature is not seen in the other four species.

Furthermore, Symplocos myrtacea belongs to the Symplocaceae family, and its stamens are longer than those of other species, protruding significantly from the petals (or corolla lobes). This is also not seen in the other four species.

Deutzia crenata belongs to the Hydrangeaceae family, and among them it may be said to be the most similar to Styrax japonica. However, unlike Styrax japonica, its petals do not open straight down, but rather open to the side or diagonally downwards, and it can be distinguished by the dense hairs on its calyx.

What are the differences between Deutzia, Deutzia crenata, and Deutzia gracilis? We'll explain how to distinguish between similar species! Could Deutzia be the origin of hedges?

Deutzia, Deutzia gracilis, and Deutzia crenata all belong to the Deutzia genus of the Hydrangeaceae family. It is believed that their name, "Utsugi" (hollow tree), comes from the fact that, except for the young branches, the inside of the branches is hollow. In Japan, they have a history of being planted as a guide for rice planting, and are also said to be the origin of hedges...

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There are other differences in leaf shape as well, but we will omit the detailed differences here. Please refer to the photos.

References

Hayashi, Masayuki. 2019. Tree Leaves: Expanded and Revised Edition - Identifying 1300 Species Through Real-Life Scans. Yama-kei Publishers, Tokyo. 824pp. ISBN: 9784635070447

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Ohashi, Hiroyoshi; Kadota, Yuichi; Murata, Hitoshi; Yonekura, Koji; and Kihara, Hiroshi. 2017. Wild Plants of Japan (Revised New Edition, Vol. 4 Malvaceae to Apocynaceae). Heibonsha, Tokyo. 608pp. ISBN: 9784582535341

RBG Kew. 2023. The International Plant Names Index and World Checklist of Vascular Plants. Plants of the World Online. http://www.ipni.org and https://powo.science.kew.org/

Fukatsu, Tadashi & Kobayashi, Yoshio. 1993. The Origin of Tree Names. Tokyo Shoseki, Tokyo. 290pp. ISBN: 9784487722310

Ardisia japonica, Ardisia crenata, Ardisia japonica, and Ardisia trifoliata all belong to the genus Ardisia in the family Primulaceae. They grow wild in evergreen broad-leaved forests, but are also widely cultivated as ornamental shrubs, along with Ardisia crenata of the family Chloranthaceae, because they bear red, spherical fruits in autumn and winter. They are particularly popular in Japan. However, since the fruits of all these plants are almost identical in shape, some people may not be able to tell the difference. However, if you pay close attention to the size of the trees and the shape of the leaves, they are relatively easy to distinguish. The serrations on the leaf margins of Ardisia crenata are enlarged, forming a state called "leaf nodules," which are in symbiosis with bacteria. While it was once thought that this role was for nitrogen fixation, it is now believed that it is to supply defensive secondary metabolites and growth factors. This article will explain the classification of the genus Ardisia.

What are Ardisia japonica, Ardisia crenata, Ardisia crenata, and Citrus tachibana?

Ardisia japonica, also known as Japanese laurel, is an evergreen shrub distributed in Hokkaido (southwestern part), Honshu, Shikoku, Kyushu, and the Tokara Islands in Japan; as well as in Korea and southern China, mainly growing on the forest floor of evergreen broad-leaved forests (Kanagawa Prefecture Flora Survey Association, 2018).

Ardisia pusilla, also known as vine jasmine, is distributed in southern Hokkaido to Kyushu in Japan, as well as in Korea, China, Taiwan, the Philippines, and Thailand. It is an evergreen shrub that grows in evergreen broad-leaved forests (Hayashi, 2019).

Ardisia crenata, also known as Manryo, is an evergreen shrub distributed throughout Japan (west of the Kanto region), Shikoku, Kyushu, and the Ryukyu Islands; and East Asia, mainly growing in evergreen broad-leaved forests.

Ardisia crispa, also known as the Chinese orange tree, is an evergreen shrub distributed in Honshu (west of the Kanto region), Shikoku, Kyushu, and the Ryukyu Islands in Japan; as well as in China and Taiwan, growing in evergreen broad-leaved forests.

Both belong to the genus Ardisia in the family Primulaceae, and are evergreen shrubs that are widely cultivated for ornamental purposes, along with plants like Ardisia crenata (a member of the Chloranthaceae family), because they bear red, spherical fruits from autumn to winter. They are especially often seen at Shinto shrines and Buddhist temples.

Taxonomically, the genus Ardisia is distinguished from other genera in the Primulaceae family by its terminal or axillary inflorescence, saucer-shaped and deeply lobed corolla with spirally overlapping corolla lobes, superior ovary, and single, spherical seed.

However, distinguishing between the four types mentioned above may be difficult without close observation.

What are the differences between Ardisia japonica, Ardisia crenata, Ardisia crenata, and Citrus tachibana?

There are eight species of Ardisia genus in Japan, but this time we will focus on four of the most common species found on the mainland.

These four species are difficult to distinguish if you only look at their red, spherical fruits, but they are relatively easy to differentiate if you pay close attention to the size of the trees and the shape of the leaves (Kanagawa Prefecture Flora Survey Association, 2018; Hayashi, 2019).

First, Ardisia japonica and Ardisia crenata grow to a height of 5-30 cm, have stolons, and their above-ground parts are unbranched, with leaves arranged somewhat whorled at the top of the stem. In contrast, Ardisia crenata and Citrus tachibana grow to a height of over 30 cm, lack stolons, have upright above-ground parts, and their leaves are arranged alternately.

To put it simply, Ardisia japonica and Ardisia crenata only grow to be quite small.

Furthermore, the leaves also exhibit distinctive characteristics: Ardisia japonica and Ardisia crenata lack internal glandular dots on the leaf margins, while Ardisia crenata and Citrus tachibana also lack internal glandular dots on the leaf margins.

The term "internal glandular dots" might be confusing, but in Ardisia crenata and Citrus tachibana, you can observe tiny, dot-like holes on the leaf margins. These are the holes that are being referred to.

Regarding Ardisia japonica and Ardisia crenata, Ardisia japonica has no long hairs on its leaves and stems, its serrations are fine, and its stolons do not have leaves, while Ardisia crenata has long hairs on its leaves and stems, its serrations are coarse, and its stolons do have leaves.

The shape of the leaves makes it obvious.

Ardisia walkeri, which is distributed from southern Kanto to the Chugoku and Kyushu regions, has long hairs but many serrations.

Regarding Ardisia crenata and Citrus tachibana, Ardisia crenata has oblong leaves, a stem that branches at the top, and terminal, sessile inflorescences on the branches, while Citrus tachibana has broadly lanceolate leaves that gradually taper to a point, a stem that hardly branches, and stalked inflorescences that emerge from the leaf axils.

However, this is a strict distinction, and you don't need to look that closely to distinguish between them, as only Ardisia crenata has thick, finely serrated edges on its leaves, so you shouldn't get confused.

What kinds of varieties and cultivars are there?

Varieties and cultivars also exist for Ardisia japonica, Ardisia crenata, Ardisia crenata, and Citrus tachibana (Ohashi et al., 2017).

Ardisia japonica f. albifructa is a variety of Ardisia japonica with white fruits.

Ardisia japonica var. angusta is a variety of Ardisia japonica with narrow, oval leaves, distributed in Izu Oshima, Yakushima, and Taiwan.

Ardisia japonica var. angusta f. leucocarpa is a variety of Ardisia japonica distributed on Izu Oshima Island, characterized by its narrowly oval leaves and white fruits.

Ardisia pusilla var. liukiuensis is a variety of Ardisia pusilla distributed in Okinawa, and is generally larger, reaching a height of nearly 30 cm.

Ardisia crenata f. leucocarpa is a variety of Ardisia crenata with white fruits.

Ardisia crenata f. xanthocarpa, also known as "Kimino Manryo," is a variety of Ardisia crenata with yellow fruits.

Ardisia crispa f. leucocarpa is a variety of Ardisia crispa with white fruit.

Ardisia crispa f. xanthocarpa is a variety of Ardisia crispa with yellow fruit.

Ardisia crispa var. caducipila is a variety of Ardisia crenata that is distributed in Honshu (Wakayama Prefecture) and Kyushu (Yakushima Island) and has small bristles on the petioles and underside of the leaves when young.

Is it a lie that Ardisia crenata fixes nitrogen?

Ecologically, the genus Ardisia is known to harbor the genus Burkholderia, a type of eubacteria, on the leaf margins (Yang & Hu, 2022).

This is particularly noticeable with Ardisia crenata; the edges of its leaves are serrated and wavy, but these serrated parts become enlarged, forming what is called a "leaf nodule."

This contains Burkholderia, and this relationship is thought to be one-to-one, having co-evolved. In the case of Ardisia crenata, it contains the species Burkholderia crenata.

Previously, due to low identification accuracy, it was thought that a completely different species of bacteria was present. Because this bacteria was a nitrogen-fixing bacterium capable of utilizing nitrogen from the air, the idea that "Ardisia crenata can fix nitrogen from its leaves" was temporarily established. Since nitrogen is an essential element for protein formation, the ability to fix nitrogen is considered a special characteristic.

However, it has now been identified as belonging to the genus Burkholderia, and while some species in this genus are capable of nitrogen fixation, it has become clear that species that live in symbiosis with the genus Ardisia do not perform nitrogen fixation.

Therefore, it is believed that species in the Ardisia genus, including Ardisia crenata, are unable to fix nitrogen from their leaves.

Instead, the genus Burkholderia has been shown to supply defensive secondary metabolites and growth factors to the genus Ardisia, which cannot grow beyond the seedling stage without Burkholderia (Carlier et al., 2016).

Although they don't fix nitrogen, the genus Burkholderia is still considered essential for the genus Ardisia.

References

Carlier, A., Fehr, L., Pinto-Carbó, M., Schäberle, T., Reher, R., Dessein, S., … & Eberl, L. 2016. The genome analysis of Candidatus Burkholderia crenata reveals that secondary metabolism may be a key function of the Ardisia crenata leaf nodule symbiosis. Environmental Microbiology 18(8): 2507-2522. https://doi.org/10.1111/1462-2920.13184

Hayashi, Masayuki. 2019. Tree Leaves: Expanded and Revised Edition - Identifying 1300 Species Through Real-Life Scans. Yama-kei Publishers, Tokyo. 824pp. ISBN: 9784635070447

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Ohashi, Hiroyoshi; Kadota, Yuichi; Murata, Hitoshi; Yonekura, Koji; and Kihara, Hiroshi. 2017. Wild Plants of Japan (Revised New Edition, Vol. 4 Malvaceae to Apocynaceae). Heibonsha, Tokyo. 608pp. ISBN: 9784582535341

Yang, CJ, & Hu, JM 2022. Molecular phylogeny of Asian Ardisia (Myrsinoideae, Primulaceae) and their leaf-nodulated endosymbionts, Burkholderia sl (Burkholderiaceae). PloS One 17(1): e0261188. https://doi.org/10.1371/journal.pone.0261188

Primroses (Primula japonica), Japanese primroses (Primula japonica), and Japanese primroses (Primula sieboldii) are all native perennial plants belonging to the Primulaceae family and Primula genus. Their flowers are similar in shape and are usually pink, leading to confusion among the three species. However, distinguishing them is relatively easy by examining the shape of their leaves. It's important to note, however, that the Primula genus includes many species, both wild and cultivated, so it's crucial not to confuse them. This article will explain the classification of Primroses, Japanese primroses, and Japanese primroses.

What are Primula japonica, Primula sieboldii, and Primula japonica?

Primula japonica, also known as the nine-petaled primrose, is a perennial herb distributed in Hokkaido, Honshu, and Shikoku in Japan, growing in wetlands in mountainous areas.

Primula sieboldii, also known as the Japanese primrose (Sakurasou), is a perennial plant found in Hokkaido, Honshu, and Shikoku in Japan; northeastern China; the Korean Peninsula; and eastern Siberia. In Japan, it is a classic horticultural plant, with hundreds of varieties developed during the Edo period. However, in modern horticulture, it is often confused with completely different species such as Primula x polyantha, Primula x juliana, and Primula malacoides, which are introduced species.

Primula kisoana, also known as Kakkosou (勝紅草), is a perennial herb distributed in Honshu, Japan (Gunma Prefecture), and grows in the undergrowth of mountain forests.

All three species belong to the genus Primula in the family Primulaceae and are native perennial herbs to Japan. Their flower shapes are similar, with a long, slender corolla that opens into five lobes at the top. They also share the characteristics of Primula species, such as erect stems and basal leaves. Therefore, distinguishing them can be difficult. All three species listed here have pink corollas.

What are the differences between Primula japonica, Primula sieboldii, and Primula japonica?

There are 14 known species of the genus Primula in Japan alone, and there are also cultivated varieties, so it is not possible to strictly introduce all the distinguishing features of all species here. However, the three species listed here are easy to distinguish (Ohashi et al., 2017; Kanagawa Prefecture Flora Survey Association, 2018). Many other species of Primula grow locally in specific regions.

First, there is a difference in that Primula japonica has no hairs on both sides of its leaves and has glandular powdery material on the underside, while Primula japonica and Primula sieboldii have hairs on both sides of their leaves and do not have glandular powdery material on the underside.

This should be obvious at a glance.

Regarding primroses and kale, the difference lies in the shape of their leaves: primroses have oval leaves with double serrations along the margins, while kale has broadly circular leaves with a heart-shaped base, shallow, irregular palmate incisions along the margins, and even finer serrations.

This is also immediately obvious. In both cases, the leaves are crucial for distinction. While there are some slight differences in the flowers, it's important to carefully record the leaves.

In addition, there is a known variety of Primula kisoana called Primula kisoana var. shikokiana, which is distributed in Tokushima, Kagawa, and Ehime prefectures in Shikoku. It grows in the undergrowth of trees in mountainous areas, and unlike the base variety, its sepals are long, measuring 1.2 to 1.5 cm, and the throat of the flower is yellowish.

References

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Ohashi, Hiroyoshi; Kadota, Yuichi; Murata, Hitoshi; Yonekura, Koji; and Kihara, Hiroshi. 2017. Wild Plants of Japan (Revised New Edition, Vol. 4 Malvaceae to Apocynaceae). Heibonsha, Tokyo. 608pp. ISBN: 9784582535341

In horticulture, the term "Abutilon" is frequently used and usually refers to a specific species rather than just one. However, this has become somewhat confusing. In horticulture, it refers to three species: Abutilon umbellatum, Abutilon humile, and Abutilon variegata. In academic terms, it refers to all members of the genus Abutilon, excluding Abutilon umbellatum and Abutilon humile. This is because the scientific names have been changed. Of the three Abutilon species used in horticulture, Abutilon umbellatum and Abutilon humile can be distinguished by the shape of their leaves and flowers. Abutilon variegata is a hybrid and therefore possesses characteristics that are intermediate between the two species mentioned above. This article will explain the classification of Abutilon umbellatum, Abutilon humile, and Abutilon variegata.

What is Abutilon?

First, what kind of plant does "Abutilon" refer to? This term usually refers to a specific species, not just one type of plant.

However, the term "abutilon" has different meanings depending on the field, making it quite confusing.

In the field of horticulture, the term "Abutilon" usually refers to three species: Callianthe megapotamica, Callianthe picta, and Abutilon x hybridum.

On the other hand, in the academic field, "Abutilon" refers to a group of plants belonging to the genus Abutilon in the Malvaceae family. According to the latest classification, it does not include Abutilon japonica or Abutilon humilis, but is a general term for plants such as Abutilon theophrasti and Abutilon indicum.

The reason for this situation is that, although in the academic field, studies in 2012 and 2014 moved Abutilon and Abutilon to different genera (Jørgensen et al., 2014), this change has not been widely disseminated in the horticultural field. Even in the academic field, many people are still unaware of this change in scientific names, and it may be some time before the meaning of "Abutilon" becomes consistent.

What are *Floating Starberry*, *Scarlet Starberry*, and *Variegated Starberry*?

From here, we will consider the differences between the three species commonly referred to as "Abutilon" in horticulture.

Callianthe megapotamica, also known as Tyrolean lamp, is an evergreen shrub native to southern Brazil (RBG Kew, 2023) that grows in riparian forests, riparian forests, and mixed forests. It has been introduced to Bolivia and the Madeira Islands and is cultivated worldwide, including Japan, for its interesting flowers and fruits. Abutilon megapotamicum is a synonym (former scientific name). It flowers from June to October.

Callianthe picta, also known as the "scarlet flower," is an evergreen shrub native to northern Argentina, southern Brazil, Paraguay, and Uruguay, growing in woodlands. It was introduced to the Madeira Islands and is cultivated as an ornamental plant worldwide, including in Japan. Abutilon pictum is a synonym (former scientific name). It flowers from April to July.

Abutilon x hybridum, also known as variegated abutilon, is an evergreen shrub of unknown origin, a hybrid of the genus Abutilon or Callianthe, created for horticultural purposes. It has been suggested that Abutilon japonica or Epipactis thunbergii may have been used in this hybrid, but this is not well understood. There are so many theories that we will omit the details here. Its scientific name may also be changed to that of the genus Callianthe in the future. It flowers from June to October.

Both are evergreen shrubs belonging to the genus Callianthe in the Malvaceae family, and are cultivated in Japan for ornamental purposes. They share the common feature of palmate venation (several main veins running palmately from the base of the leaf), which is common in the Malvaceae family, and their drooping flowers are also similar in shape, so they may sometimes be confused with each other.

What are the differences between *Aster tataricus*, *Aster savatieri*, and *Aster savatieri*?

First of all, *Lysimachia japonica* and *Lysimachia japonica* are completely different species, so the differences are clear (Hayashi et al., 2019).

Both species have leaves with 3 to 5 lobes, but the difference lies in their lobes: in *Atragalus sieboldiana*, the lobes are shallow (shallowly lobed), while in *Atragalus membranaceus*, the lobes are not quite deep, but are considerably deeper (moderately lobed). * Atragalus membranaceus* leaves give the impression of being similar to maple leaves.

Regarding the flowers, in *Acer palmatum*, the calyx is sac-like, large, and conspicuously red, with only a small portion of the yellow corolla visible from the outside, whereas in *Acer palmatum*, the calyx is not sac-like but green, and the corolla is large and conspicuously red.

In other words, in *Aster tataricus*, the sepal is the organ that most conspicuously attracts insects, whereas in *Scarlet japonica*, it is the corolla. This difference is quite significant.

The problem lies with the variegated Abutilon. There is considerable variation depending on the variety, and there is no definitive characteristic.

The leaves vary from shallowly lobed to moderately lobed, and the flowers also vary in sepal structure (from sac-like to non-sac-like) and corolla size (from small to large).

However, in the case of horticultural varieties found in Japan, if they exhibit a mixture of characteristics from both *Avena cuneata* and *Schizocodon soldanelloides*, it is reasonable to consider them as *Avena cuneata* variegata. As mentioned above, the flower and calyx colors are clearly defined in *Avena cuneata* and *Schizocodon soldanelloides*, so those with other coloration can also be considered *Avena cuneata* variegata.

Please note that while the Japanese name "Fuiriabutilon" (meaning "variegated") might suggest it's always variegated, it's not always the case. It's not a very appropriate name.

References

Hayashi, Masayuki. 2019. Tree Leaves: Expanded and Revised Edition - Identifying 1300 Species Through Real-Life Scans. Yama-kei Publishers, Tokyo. 824pp. ISBN: 9784635070447

Jørgensen, PM, Nee, MH & Beck., SG 2014. Catálogo de las plantas vasculares de Bolivia. Monographs in Systematic Botany from the Missouri Botanical Garden 127: 1-1741. ISSN: 0161-1542, ISBN: 9781930723719, https://www.mbgpress.org/product-p/msb-127.htm

RBG Kew. 2023. The International Plant Names Index and World Checklist of Vascular Plants. Plants of the World Online. http://www.ipni.org and https://powo.science.kew.org/

Both the Bodhi tree (Tilia japonica) and the large-leaved Bodhi tree (Tilia maximowicziana) are deciduous trees belonging to the genus Tilia in the Malvaceae family. Although they have different origins, they are both cultivated in cities throughout Japan, and their leaf shapes are very similar, so those who have never seen them may not be able to distinguish them. However, there are significant differences not only in the size of the leaves but also in the length of the petioles. A closely related species in the same genus is the Japanese linden (Tilia japonica), but this can be distinguished by the brown hairs in the vein axils on the underside of the leaves and the shape of the flowers. They are often confused with the Indian Bodhi tree due to their names, but the Indian Bodhi tree belongs to the Moraceae family and has completely different leaf and flower shapes. Originally, the tree under which Gautama Siddhartha (Buddha) attained enlightenment was the Indian Bodhi tree, but because the Indian Bodhi tree does not grow in Japan, this species was imported from China as a substitute for planting in temples, resulting in the names being reversed. The inflorescences of the Bodhi tree and the large-leaved Bodhi tree hang downwards, and the flowers are small and white, but they have a strong scent that seems to attract many bees. The fruit is a nut, and there are bracts at the base of the inflorescence. When it falls, it rotates, moving away from the mother tree and thus dispersing the seeds. This article will explain the classification, morphology, pollination ecology, and seed dispersal of linden and large-leaved linden.

What are the linden tree and the large-leaved linden tree?

The Bodhi tree (Tilia miqueliana) is a deciduous tree distributed in China (Wu et al., 2007). In Japan, it is cultivated mainly in temples as a substitute for the sacred Indian Bodhi tree.

Tilia mandshurica, also known as the large-leaved linden tree, is distributed in Hokkaido, the Tohoku and Hokuriku regions of Honshu, and the northern part of the Kanto region of Japan. It is a deciduous tree that grows in deciduous forests in mountainous areas (Mogi et al., 2000). It is sometimes cultivated as a park tree or street tree in colder regions.

Both are deciduous trees belonging to the genus Tilia in the Malvaceae family. Although they have different origins, they share the commonality of being cultivated in cities across Japan. Their names are also similar, and those who have never seen them may not be able to distinguish between them. They also share the characteristic of having leaves that can be heart-shaped, and a venation pattern called "palmate venation," where the veins spread out from the base of the petiole throughout the leaf.

What are the differences between the Japanese linden (Tilia japonica), the large-leaved linden (Tilia japonica), and the Japanese linden (Tilia japonica)?

Before discussing the differences between the two species, it's worth noting that the same genus includes a plant called Tilia japonica (Japanese linden tree). Tilia japonica is endemic to Japan, distributed across Hokkaido, Honshu, Shikoku, and Kyushu, and is a deciduous tree that grows from mountain ridges to streams.

What are the differences between the Japanese linden tree (Tilia japonica), the large-leaved linden tree (Tilia japonica), and the Japanese linden tree (Tilia japonica)?

First, the leaf shape differs: in the linden tree, the leaves are distorted heart-shaped with few wrinkles on the upper surface, while in the Japanese linden, they are triangular to heart-shaped, and in the large-leaved linden, the upper surface of the leaves is very wrinkled (Hayashi, 2019).

In linden trees, there are clusters of brown hairs in the vein axils on the underside of the leaves, and these are particularly noticeable at the base of the petiole, where the leaves appear to be covered in brown hairs. This is absent in Japanese linden trees, and while it is common in large-leaved linden trees, it remains light brown.

The most distinctive feature is the flowers: in the linden tree, the stamens clearly protrude outward from the petals, while in the Japanese linden and large-leaved linden, the stamens are not as long and curve inward.

What is the difference between a linden tree and an Indian linden tree?

The Indian fig tree (Ficus religiosa) is another species that is often mistaken for the fig tree due to its name. The Indian fig tree is a semi-deciduous tree distributed from India to Southeast Asia.

The Indian fig tree is taxonomically completely different from the common fig tree (Tilia japonica). As mentioned above, the common fig tree belongs to the genus Tilia, while the Indian fig tree belongs to the genus Ficus in the family Moraceae.

Therefore, there are many differences. First, regarding the leaves, the Indian fig (Ficus lyrata), like other fig species, has thick, entire leaves with very long, tail-like tips that can extend more than a third of the leaf blade, whereas the leaves of the linden tree (Tilia japonica) and other Tilia species are thinner, serrated, and while the tips are tail-like, they are quite short.

The flowers differ further; the Indian fig tree, like many fig species, produces special flowers called "syconium" or "syconium" that resemble fruits, while the linden tree and other Tilia species have typical open flowers.

While the Indian linden tree, like its relatives the banyan tree and the fig tree, can become a "strangler fig," the fact that this doesn't happen with the Tilia genus is a significant advantage.

What's the difference between a banyan tree and a fig tree? Why is it called the "strangler fig"? Where are the flowers? Only one type of insect visits the flowers!? Where are the real fruits? It's an important food source for bats!?

The Japanese banyan tree (Ficus microcarpa) and the Japanese Ficus microcarpa (Ficus sylvestris) are known as two "strangler figs" in southern Japan, both producing drooping aerial roots and forming flower receptacles. Ecologically, they are similar, and it can be difficult to distinguish between them. However, there are significant differences in leaf venation and leaf length between the two. Also, regarding aerial roots...

ecological-information.com

So why do they have such similar names despite being so different?

The Japanese word for linden tree, Bodhiju, is written with the kanji characters "菩提樹," where "Bodhi" is a transliteration of a Sanskrit word meaning the state of enlightenment attained by Buddha. It originates from the fact that it was the tree under which Gautama Siddhartha (Shakyamuni), the founder of Buddhism, attained enlightenment, although originally that tree was the Indian linden tree (Iwasa, 1982; Tsumega, 1990; Kurita, 2008).

However, since the Indian fig tree is native to the tropics and does not grow in Japan, fig trees imported from China were used as a substitute for planting in temples. This resulted in the confusing situation of the Japanese names being reversed. There is a theory that it was Eisai, the founder of the Rinzai school of Zen Buddhism, who brought them back (Kurita, 2008). If so, this would have been during the Southern Song dynasty in China and the Heian period in Japan.

However, it's unclear why the "Bodhi tree" was chosen from among the many plants. Perhaps it was simply because its leaves resembled those of a tail (Tsumaga, 1990), but this explanation is not very convincing and remains unclear in my research.

It is also considered a sacred tree in Hinduism (Iwasa, 1982).

What is the difference between a linden tree and a large-leaved linden tree?

There are many differences between the Japanese linden tree and the large-leaved linden tree (in the broad sense) (Hayashi, 2019).

First, as mentioned above, the Bodhi tree (Ficus microcarpa) is native to China and is mainly planted around temples, while the large-leaved Bodhi tree (Ficus serrata) grows wild in Japan. Therefore, wild specimens are likely to be large-leaved Bodhi trees. However, since large-leaved Bodhi trees are also sometimes planted, it may be difficult to distinguish them from planted specimens.

In terms of morphological differences, as the name suggests, the leaf blade size of the Japanese linden is 5-10 cm, while that of the large-leaved linden is considerably larger, at 7-18 cm.

A more striking difference is the length of the petioles: while those of the common linden tree are only 2-4 cm long, those of the large-leaved linden tree are 4-7 cm long, making them noticeable even from a distance. I think this is a good difference, as there is no overlap between the two species.

While the leaves of the Japanese linden tree (Tilia japonica) are triangular to heart-shaped, those of the large-leaved linden tree (Tilia maximowicziana) are round to heart-shaped.

Furthermore, while the large-leaved linden has clusters of light brown hairs in the vein axils on the underside of its leaves, the common linden lacks this feature.

While the flowers of the Japanese linden (Tilia japonica) tend to be yellowish-brown, those of the large-leaved linden (Tilia maximowicziana) are usually white to pale yellow. However, the morphological differences are minimal, making it difficult to use this distinction for species identification.

In addition, there is a known species called Tilia mandshurica var. mandshurica, which is distributed in the Chugoku region and Oita Prefecture of Japan, as well as the Korean Peninsula, Northeast China, and Russia (Siberia). However, although this species has stellate hairs covering the entire underside of its leaves, like Tilia maximowicziana, it completely lacks the light brown hair clusters in the vein axils on the underside of the leaves that are present in Tilia maximowicziana.

What are the varieties of the large-leaved linden tree?

Two varieties of the large-leaved linden (in the broad sense) are known.

The underside of the leaves of Tilia maximowicziana (in the narrow sense) is densely covered with stellate hairs, giving it a whitish appearance.

The underside of the leaves of Linden moss var. yesoana has sparse stellate hairs and is somewhat green.

What is the structure of a flower?

Like many other species in the Tilia genus, the flowers of the Japanese linden (Tilia japonica) and the large-leaved Japanese linden (Tilia japonica) hang down in drooping cymose inflorescences, bearing numerous small white to yellow flowers. While the shape of the flowers themselves is not particularly unusual, the presence of bracts at the base of the inflorescence is distinctive. These are used during fruit development.

The linden tree blooms in June. Bracts are borne in the leaf axils at the tips of the branches, and cymose inflorescences hang down from near the center of the bracts, bearing 3 to 12 (up to 20) flowers. The cymose inflorescences are 6 to 10 cm long. The bracts have short petioles (sometimes sessile), are spatulate in shape, 5 to 8 (up to 12) cm long, have a blunt apex, and a narrowly cuneate base, with stellate hairs on both surfaces and densely covering the underside. The flowers are pale yellow and fragrant. The pedicels are 4 to 6 cm long, and the pedicels are 8 to 12 mm long. The sepals are 5 to 6 mm long. The petals are slightly longer than the sepals. There are 5 stamens and 5 staminodes.

The large-leaved linden tree flowers from June to July. It hangs down cymose inflorescences 6-10 cm long from the sides of the base of the petioles, bearing more than ten pale yellow flowers at the end. Narrowly oblong involucral bracts are fused to the axis of the inflorescence. The involucral bracts are 5-8 cm long when in flower, densely covered with stellate hairs on both sides, and have short stalks 2-5 mm long at the base. There are five sepals, lanceolate in shape, 6-7 mm long, with pointed tips, and densely covered with long hairs on the inner surface and stellate hairs on the back. There are five pale yellow petals, narrowly oblong in shape, about 8 mm long, with slightly blunt tips. There are many stamens, about 5 mm long, and they are free. Inside the petals are five staminodes, which are spatulate, petal-like, and shorter than the petals. The ovary has five chambers, each containing two ovules, and the style is slender and elongated, with the stigma shallowly divided into five lobes.

How is pollination done?

The linden tree (Tilia japonica) and the large-leaved linden tree (Tilia maximowicziana) have fragrant flowers and produce abundant nectar, clearly indicating that they are insect-pollinated, just like other members of the Tilia genus.

In literature, there are records of the beetle Ceresium sinicum visiting linden trees (Ikeda, 2016). There are also records of European honeybees visiting (Sasaki, 2010), but since European honeybees are an invasive species, they would not contribute to pollination in the wild.

On the internet, the Kyoto University Museum database contains specimens of a species of mud dauber wasp and a species of ancient bumblebee collected from a linden tree (Kyoto University Museum, 2023), and one blog features a photograph of a yellow-breasted bumblebee visiting the tree (waiwai, 2010).

In literature, there are records of bumblebees such as the Japanese bumblebee (Bombus ignitus) and the small bumblebee (Bombus spp.) frequently visiting the Japanese linden tree (Tilia japonica) (Mizui, 1993). There are also records of European honeybees visiting the tree, and honey made from its single-flower nectar is sometimes sold (Sasaki, 2010; Masaka et al., 2013). Although European honeybees are an introduced species, they do provide benefits to humans.

In summary, while longhorn beetles are an exception, it seems that many types of bees are attracted to these flowers. The reason why, despite the flowers not having any special structure, is not fully understood, but the secret likely lies in their scent. A Chinese study detected a total of 70 volatile components in the flowers of winter linden (T. cordata), linden, and silver linden (T. tomentosa), and identified 43 aromatic compounds (Bao & Shen, 2022). These may be what strongly attracts bees.

What is the structure of the fruit?

The fruits of the Japanese linden (Tilia japonica) and the large-leaved linden (Tilia japonica) are also nuts, as is common with many other species in the Tilia genus. A nut is a fruit in which a hard, woody pericarp encloses a single seed and does not split open.

However, the unique feature is the presence of bracts at the base of the inflorescence; in the large-leaved linden, the flowers eventually elongate to a length of 6-10 cm when they develop into fruits.

The linden tree's nuts are spherical, 7-8 mm in diameter, hard, and densely covered with fine, stellate hairs on their surface.

The nuts of the large-leaved linden tree are spherical or oval in shape, 10-15 mm long, with five ridges, and densely covered with short, grayish-white hairs. They mature around October and contain a single seed without splitting open.

What are the seed dispersal methods?

The genus Tilia is dispersed by wind through its bracts (Manchester, 1994), and this is thought to be the case for Tilia japonica and Tilia maximowicziana as well (Azuma & Yasuda, 1989; Nonoda et al., 2008).

However, unlike many wind-dispersed plants where the fruit or seeds fall to the ground and are then carried away by the wind, in the genus Tilia, the inflorescence below the bracts is separated, and the distorted bracts, caught in the wind's resistance, rotate as they fall, slowly moving through the air and away from the mother tree.

In other words, it can be said that this is a seed dispersal method very similar to that of samaras of genera such as maple, hornbeam, cypress, fir tree, and tulip tree (Johnson, 1988; Azuma & Yasuda, 1989). This seed dispersal method seems to be possible precisely because it is a tall tree.

References

Azuma, A., & Yasuda, K. (1989). Flight performance of rotary seeds. Journal of Theoretical Biology, 138 (1), 23-53. https://doi.org/10.1016/S0022-5193(89)80176-6

Bao, W., & Shen, Y. (2022). Dynamic Changes on Floral Aroma Composition of the Three Species from Tilia at Different Flowering Stages. Horticulturae, 8 (8), 719. https://doi.org/10.3390/horticulturae8080719

Hayashi, Masayuki. (2019). Tree Leaves: Expanded and Revised Edition - Identifying 1300 Species Through Real-Life Scans. Yama-kei Publishers. ISBN: 9784635070447

Ikeda, Dai. (2016). Additional records of *Tetsuirohimekamikiri* from Hyogo Prefecture. *Kiberihamushi*, 38 (2), 48. ISSN: 1884-9377, https://www.konchukan.net/pdf/kiberihamushi/Vol38_2/kiberihamushi_38_2_48.pdf

Iwasa, Shunkichi. (1982). Sketches of Tropical Crops (VIII): Religious Trees. Tropical Forestry, 63, 33-36. https://doi.org/10.32205/ttf.0.63_33

Johnson, WC (1988). Estimating dispersibility of Acer, Fraxinus and Tilia in fragmented landscapes from patterns of seedling establishment. Landscape Ecology, 1, 175-187. https://doi.org/10.1007/BF00162743

Kurita, W. (2008). This Month's Tree: The Linden. Green Power, 353, 3. ISSN: 0389-0988, https://doi.org/10.11501/12524798

Kyoto University Museum. (July 1, 2023). Insects - Natural History Specimens. Kyoto University Museum website. https://www.museum.kyoto-u.ac.jp/collection/Konchu/html/index_Konchu.html

Manchester, SR (1994). Inflorescence bracts of fossil and extant Tilia in North America, Europe, and Asia: patterns of morphologic divergence and biogeographic history. American Journal of Botany, 81 (9), 1176-1185. https://doi.org/10.1002/j.1537-2197.1994.tb15612.x

Masaka, K., Sato, T., & Tanahashi, Ikuko. (2013). Actual utilization of tree nectar sources by beekeeping: Diversity and regional characteristics in Hokkaido. Journal of the Japanese Forestry Society, 95 (1), 15-22. https://doi.org/10.4005/jjfs.95.15

Tsumega, Kaneo. (1990). National Flowers of the World. Hoikusha. ISBN: 9784586507917, https://doi.org/10.11501/13645920

Mizui, Norio. (1993). Ecological studies on seed propagation of deciduous broad-leaved trees. Research Report of Hokkaido Forestry Experiment Station, 30, 1-67. ISSN: 0910-3945, https://agriknowledge.affrc.go.jp/RN/2030500320

Mogi, Toru; Ota, Kazuo; Katsuyama, Teruo; Takahashi, Hideo; Shirokawa, Shiro; Yoshiyama, Hiroshi; Ishii, Hidemi; Sakio, Hitoshi; and Nakagawa, Shigetoshi. (2000). Flowers Blooming on Trees: Polypetalous Flowers (Vol. 2, 2nd edition). Yama-kei Publishers. ISBN: 9784635070041

Nonoda, S., Shibuya, M., Saito, H., Ishibashi, S., & Takahashi, M. (2008). Invasion and growth process of broad-leaved trees in fir plantations and the effects of thinning. Journal of the Japanese Forestry Society, 90(2), 103-110. https://doi.org/10.4005/jjfs.90.103

Sasaki, Masami. 2010. The World of Flowers as Seen by Bees: Nectar-Producing Plants of the Four Seasons and Gifts from Honeybees. Kaiyusha. ISBN: 9784905930273

waiwai. (June 19, 2010). Linden tree and bumblebee. Cat's Days. http://nekobiyori.cocolog-nifty.com/days/2010/06/post-4d5a.html

Wu, ZY, Raven, PH, & Hong, DY (Eds.). (2007). Flora of China (Vol. 12 Hippocastanaceae through Theaceae). Science Press, and Missouri Botanical Garden Press. ISBN: 9781930723641

Rumex japonicus, Rumex longifolius, Rumex crispus, and Rumex serrata all belong to the genus Rumex in the family Polygonaceae. Originally, only Rumex japonicus was distributed in Japan, but multiple species have invaded and become extremely common weeds. They all share a preference for disturbed ground, and are often found growing together. Furthermore, the appearance of their flowers and fruits is very similar, making identification difficult without careful comparison. They can be distinguished from sorrel species by the shape of their leaves and flowers. More than 10 species of Rumex have been confirmed in Japan, and accurate identification requires a field guide, but if we limit ourselves to the four most common species, the most accurate method of identification is by the shape of the "inner perianth that encloses the fruit." The flowers are very inconspicuous and small, with no distinction between the inner perianth (petals) and outer perianth (sepals). This is because they are wind-pollinated, not pollinated by insects. After pollination, the inner perianth remains, swells and flattens, and encloses the fruit (achene). This structure allows the seeds to be carried to other locations by wind and water. However, the presence of thorns (serrations) on the inner perianth and "white, knob-like protrusions" suggests the possibility of "dispersion by attachment to animals" or "dispersion by animal feeding," although this has not been adequately researched. This article will explain the classification, pollination ecology, and seed dispersal of dock species.

What are Rumex japonicus, Rumex longifolius, Rumex crispus, and Rumex serrulata?

Rumex japonicus, also known as dock (or pygmy dock), is a common perennial herb found in Hokkaido, Honshu, Shikoku, Kyushu, and the Ryukyu Islands in Japan; as well as in Korea and China, growing in wastelands, roadsides, and fields in urban areas and around human settlements.

Rumex crispus, also known as long-leaved dock, is native to Europe and has naturalized widely throughout the Eurasian continent. It is a perennial herb that grows in wastelands and roadsides in urban areas and around human settlements.

Rumex conglomeratus, also known as "wasteland dock," is native to Europe and has naturalized widely throughout Eurasia. In Japan, it was introduced during the Meiji era and is commonly found in central Honshu, growing in wastelands and roadsides in urban areas and around human settlements.

Rumex obtusifolius, also known as Ezo dock, is native to Europe and has naturalized widely throughout the world, including Japan. It is a perennial herb that grows in wastelands and roadsides in urban areas and around human settlements.

All of these species belong to the genus Rumex in the family Polygonaceae. Originally, only Rumex japonicus was found in Japan, but now several species have invaded from Eurasia and have become extremely common weeds. They also share a preference for disturbed soil, and are often found growing together. Furthermore, their flowers and fruits look very similar. Therefore, they may be easily confused if not carefully observed.

What is the difference between dock and sorrel?

Before considering these four species, it's important to note that the genus Rumex also includes other species besides the common dock (Rumex acetosa) and the dwarf sorrel (Rumex acetosella). What are the differences between these two species?

First, there is a difference between dock species (Rumex serrata) and sorrel species (Rumex acetosa). In other words, all dock species have "hermaphrodite flowers" that have both stamens and pistils, but sorrel species have two types: individuals with "male flowers" that have only stamens (male plants) and individuals with "female flowers" that have only pistils (female plants).

The female flowers of this sorrel species are very red and conspicuous, so you can spot the red inflorescence of sorrel species even from a distance. This is not the case with dock species.

In terms of leaf morphology, dock species have wedge-shaped, rounded, or heart-shaped leaf bases, while sorrel species have scaly or lanceolate leaf bases. This difference may be useful when observing plants outside of their flowering season.

In addition, the Japanese name for sorrel (suiba) is said to be "suiba" (sour leaf), derived from its sour taste. This sourness comes from oxalic acid, which is also found in dock plants, but sorrel seems to be more sour, possibly because it contains more oxalic acid. According to someone who actually compared the two, "suiba is clearly more sour" (Ayumin, 2021). Therefore, this can be used to distinguish them, but it seems that no one has confirmed whether all dock plants are not sour.

What are the differences between *Rumex japonicus*, *Rumex longifolius*, *Rumex serrata*, and *Rumex japonica*?

More than 10 species of the genus Rumex have been identified in Japan, including the sorrel species mentioned earlier, making accurate identification difficult without consulting a field guide. However, the four species listed at the beginning are the most commonly found in urban areas and are frequently encountered. Therefore, this section will explain how to distinguish between these four species. For those who want to accurately distinguish all species, please refer to Ohashi et al. (2017) or the Kanagawa Prefectural Flora Survey Association (2018).

Firstly, in Rumex japonicus, the edges of the inner perianth surrounding the fruit have prominent thorns, whereas in Rumex crispus, Rumex longifolius, and Rumex serrata, the edges of the inner perianth surrounding the fruit are entire or have only shallow serrations.

The "inner perianth surrounding the fruit" is a structure unique to the Rumex genus. It is the inner perianth that was present between the flowers, which remains after flowering and becomes thinner, with a white, knob-like projection attached to the center. This is quite noticeable even from a distance.

Regarding the remaining three species, in *Rumex crispus*, the flowers and fruits are spaced apart and arranged in whorls, so the inflorescence appears sparse, and the inflorescence and fruit clusters have bracts. In contrast, in *Rumex rotundifolia* and *Rumex longifolia*, although the flowers and fruits are also arranged in whorls, they are spaced closely together, forming a large panicle inflorescence overall, and the inflorescence and fruit clusters lack bracts.

Regarding dock (Rumex japonicus) and long-leaved dock (Rumex crispus), the difference is that in dock, the inner perianth surrounding the fruit has low serrations along the edge and a slightly pointed tip, while in long-leaved dock, the inner perianth has an entire margin with a rounded tip.

In addition, it may be possible to distinguish them based on the leaves alone, but this would be complicated due to differences between stem leaves and basal leaves, so we will omit that here. The period when the inner perianth is present is limited, but it would be desirable to confirm this point if possible.

Furthermore, these four species prefer similar environments and coexist, leading to the observation of many hybrids. If fruiting is infrequent and intermediate characteristics are present, it may be necessary to consider the possibility of a hybrid.

What is the structure of a flower?

The flowers of the Rumex genus have a similar structure to typical flowers. However, they are very inconspicuous and small, and the calyx and petals are almost indistinguishable in appearance. For this reason, the part corresponding to the calyx is often called the "outer perianth," and the part corresponding to the petals is called the "inner perianth."

Dock (Rumex rotundifolia) flowers from June to August (Wu et al., 2003). Its inflorescence is a panicle, densely arranged in multiple whorls. It is monoecious, with both hermaphroditic and female flowers. The pedicels are slender, with nodes located below the middle and clearly defined. Each flower consists of three outer perianth segments, three inner perianth segments, six stamens, and one pistil.

Rumex rotundifolia flowers from June to August, with flowers borne in long racemes that are densely arranged in multiple whorls. It is monoecious, with both hermaphroditic and female flowers. Each flower consists of three outer perianth segments, three inner perianth segments, six stamens, and one pistil. The pistil has three styles, and the stigma is finely divided.

Rumex crispus flowers from June to July. Its flower stalks are branched with long internodes, and the flowers are densely arranged in whorls at each node. The pedicels are 1-4 (up to 5) mm long. The flowers are small, with the inner perianth measuring 2-3 mm in length and 1-1.6 (up to 2) mm in width.

Rumex japonicus flowers from June to August. The flowers are borne in long racemes, arranged in whorls with spacing between tiers. It is monoecious, with both hermaphroditic and female flowers. Each flower consists of 6 perianth segments (sepals), 6 stamens, and 1 pistil.

How is pollination done?

It is known that flowers of the Rumex genus, including sorrel species, are commonly pollinated by wind (Wagatsuma et al., 1974; Zaller, 2004; CABI, 2021). In fact, airborne pollen has been discovered in Japanese research. Morphologically, the indistinguishable nature of the sepals and petals indicates a lack of appeal to insects, and the absence of nectar secretion suggests that there is no need to attract insects.

Among wind-pollinated flowers, it is classified as a "pendulous type," and because the flower stalks extend downwards, the flowers appear to droop and are easily swayed by the wind (Utsumi, 2002).

What is the structure of the fruit?

The fruits of the Rumex genus are all achenes. An achene is a fruit with a hard, membranous pericarp that dries when ripe and contains one seed in each chamber. However, as mentioned above, the three inner perianth segments enlarge during fruiting and enclose the fruit, so the shape of the fruit cannot be seen from the outside (Iwase et al., 2021). In addition, some species have "white, knob-like projections (tubercles)" on the inner perianth segments, which is also a distinctive feature, but some species, such as Rumex acetosa and Rumex chinensis, do not have these. Only one fruit (achene) is enclosed within the three inner perianth segments.

The three inner perianth segments of the dock are broadly heart-shaped, 4-5 mm long and 5-6 mm wide. All inner perianth segments have white, knob-like projections, distinct reticulate venation, a heart-shaped base, irregularly toothed margins, and an acute apex, with the teeth measuring 0.3-0.5 mm in height. The inner achenes are dark brown, glossy, broadly ovate, sharply triangular, about 2.5 mm long, with a narrow base and an acute apex.

The three inner perianth segments of *Rumex japonicus* are broadly ovate, entire, with rounded tips and a knob-like projection in the center. The size of the knob-like projection varies. The inside of the inner perianth is slightly concave, but otherwise almost flat. The achene is three-angled and brownish-red.

The three inner perianth segments of *Rumex crispus* are oblong-ovate, entire, and the central knob-like projection is often reddish. The achenes are the smallest among the *Rumex* species, measuring 1.5–2 mm in length and 1–1.6 (2) mm in width, and are dark brown.

The three inner perianth segments of *Rumex japonicus* are ovate, with a slightly elongated, pointed tip, long projections along the edges, and a knob-like projection in the center. The projections along the edges are often sparse, and the knob-like projection is usually red. The achenes are 2–2.7 mm long and 1.2–1.7 mm wide, triangular in shape, and brown to reddish-brown in color.

What are the methods for seed dispersal? There are many methods besides "wind dispersal"!

The most common seed dispersal method for the Rumex genus is wind dispersal (CABI, 2021). The three flattened inner perianth segments are carried away by the wind, spreading to various locations. This is the same method used for pollen dispersal, and by not relying on luck factors like insects or animals, it can spread very effectively in open, disturbed areas. The flattened structure is also well-suited to floating on water, so water dispersal also occurs.

However, the presence of various appendages suggests that dispersal is not simply wind-based. For example, in some species, including Rumex japonicus, the inner perianth segments have serrations. This is thought to allow them to adhere to the fur and feathers of animals (mammals and birds), including humans, enabling them to travel long distances (CABI, 2021). In other words, they act as "burrs" and disperse by attaching to animals. However, the specific animals involved are unclear. Their shape makes it seem unlikely they would adhere to human clothing.

In addition, while many species exhibit "white, knob-like protrusions" on the inner perianth segments, some species lack them. What role do these protrusions play? It seems that lighter protrusions would be preferable if they were to be carried by wind or water.

I couldn't find any proper research on this. I think there are several different ideas about this role.

Firstly, after being carried away by wind and water, seeds accumulate in the soil, but this is not always a suitable environment for their survival. Therefore, it is already known that they wait underground until they are ready to germinate, forming a "seed bank" (CABI, 2021). In one study, 83% of Rumex japonicus seeds remained viable after being buried for 21 years.

Therefore, it may exist to supply nutrients to the seeds while it is in existence as a seed bank. However, structurally, the protrusions do not appear to be in contact with the seeds, so it is unclear whether this is possible, and it is questionable whether dormancy is impossible without such a structure.

Secondly, it may serve the purpose of providing nutrients to animals that eat the seeds. In fact, it is known that the seeds are eaten by mammals such as birds and cows (CABI, 2021; Bhandari & Park, 2022). This is called "animal dispersal." In the case of birds, it is said that they will eat the fruits of the dock family if there are no other good food sources. It is also known that the ingested seeds are difficult to digest and can be dispersed through feces. Based on this fact, it is natural to think that there is something about the fruit that makes animals think, "It's delicious!"

The third reason is that it's a structure for buoyancy. The cross-section of the white, knob-like protrusions looks like cork. Perhaps having such a structure actually makes the seeds float more easily.

It is thought that one or more of these roles exist, but this has not been verified at all. They may have a great many seed dispersal methods, but which one they primarily rely on likely varies depending on the species.

References

Ayumin. [Ayumin's Weed Cafe]. (January 20, 2021). Thorough Comparison! Sorrel vs. Dock ① ~Comparing raw and boiled versions by color~ [Video]. YouTube. https://www.youtube.com/watch?v=cTcnUJvmrkQ

Bhandari, GS, & Park, CW (2022). Molecular evidence for natural hybridization between Rumex crispus and R. obtusifolius (Polygonaceae) in Korea. Scientific Reports, 12 (1), 5423. https://doi.org/10.1038/s41598-022-09292-9

CABI. (2021). Rumex obtusifolius (broad-leaved dock). CABI Compendium. https://doi.org/10.1079/cabicompendium.48064

Iwase, T., Kawana, K., & Iijima, K. (2021). Weeds in schoolyards (revised edition). National Rural Education Association. ISBN: 9784881371992

Kanagawa Prefecture Flora Survey Association. (2018). Kanagawa Prefecture Flora 2018 Electronic Edition. Kanagawa Prefecture Flora Survey Association. ISBN: 9784991053726

Ohashi, Hiroyoshi; Kadota, Yuichi; Murata, Hitoshi; Yonekura, Koji; and Kihara, Hiroshi. (2017). Wild Plants of Japan (Revised New Edition, Vol. 4: Malvaceae to Apocynaceae). Heibonsha. ISBN: 9784582535341

Utsumi, Shusaku. (2002). Why are flowers beautiful? 1. Insects and pollination. Research Bulletin of the Faculty of Education, Chiba University, 50, 441-448. ISSN: 1348-2084, https://opac.ll.chiba-u.jp/da/curator/900026751/

Yoshinori Wagatsuma, Ryuji Matsuyama, Mikiya Sato, Koji Ito, Tamiko Mizutani, and Yoko Fujisaki. (1974). Rumex acetosa and dock pollen allergy (hay fever). Allergy, 23(3), 245-246. https://doi.org/10.15036/arerugi.23.245_2

Wu, ZY, Raven, PH, & Hong, DY (Eds.). (2003). Flora of China (Vol. 5 Ulmaceae through Basellaceae). Science Press, and Missouri Botanical Garden Press. ISBN: 9781935641056

Zaller, JG (2004). Ecology and non-chemical control of Rumex crispus and R. obtusifolius (Polygonaceae): a review. Weed Research, 44 (6), 414-432. https://doi.org/10.1111/j.1365-3180.2004.00416.x

Okra and Abelmoschus manihot are both members of the Malvaceae family, genus Abelmoschus. They are often confused because they are both used by humans due to the viscosity of parts of their plants, and they share similarities in morphology, such as palmate leaves with 3 to 9 lobes, a protruding column formed by the fusion of stamens and pistils, and a white corolla. However, they can be distinguished by carefully observing the calyx-like bracts, leaves, and fruits. In terms of uses, okra is mainly eaten as an immature fruit, while the mucilage of the roots of Abelmoschus manihot has been used in the production of Japanese paper. Both species have distinctive flowers with a white corolla and a dark purple center. Self-pollination is possible, but overseas research has shown that visits by bees increase seed production. Okra fruits are usually harvested immaturely, but when ripe, they split along the ovary chamber, scattering the seeds. However, considering the usage, manual sowing is likely the most efficient method of seed dispersal. This article will explain the classification, uses, pollination ecology, and seed dispersal of okra and hibiscus.

What are okra and tororo aoi?

American okra, also known as Abelmoschus esculentus, is commonly called okra. While its origin is sometimes definitively identified as Ethiopia, its actual origin is unknown, and India has been suggested as a possibility (Benchasri, 2012; Singh et al, 2014; Mohammed et al., 2020). Wild specimens do not exist, and it is currently a cultivated perennial plant in Japan, Turkey, Iran, West Africa, Yugoslavia, Bangladesh, Afghanistan, Pakistan, Myanmar, Malaysia, Thailand, India, Brazil, Ethiopia, Cyprus, and the southern United States. However, in Japan, it cannot survive the winter and is treated as an annual. The name okra originates from the Twi word "nkrama" from Ghana. The name American okra comes from the fact that it was introduced to Japan from America around the end of the Edo period.

Abelmoschus manihot, also known as tororo-aoi (yellow okra), is a perennial or annual plant distributed in China, India, Nepal, the Philippines, and northern Thailand, growing in grasslands, along rivers, and on the edges of farms (Wu et al., 2007). The exact time of its introduction to Japan is unknown, but it is presumed to have arrived earlier, as it is depicted in wood carvings from the late Muromachi period (Masuda, 2009). Its Japanese name comes from the fact that its roots and fruits are mucilaginous and resemble tororo (grated yam or Chinese yam).

What are the differences between Japanese yam (Dioscorea japonica), Chinese yam (Dioscorea japonica), Japanese yam (Dioscorea tokoro), and bitter yam (Dioscorea japonica)? We explain how to distinguish between similar species! Why do they produce bulbils? Their reproductive strategies were diverse!

Japanese yam (Dioscorea japonica), Chinese yam (Dioscorea longa), Japanese yam (Dioscorea tokoro), and bitter yam (Dioscorea japonica) all belong to the genus Dioscorea in the family Dioscoreaceae. They produce edible tubers and bulbils, and are very common climbing perennial plants often seen in urban areas. The genus Dioscorea, also known as yam, is a group that includes a vast number of species...

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Both belong to the Malvaceae family, genus Abelmoschus, and share several similarities: some parts of the plant are sticky, their leaves are palmate with 3 to 9 lobes, their flowers have a protruding "column" (a fused structure of stamens and pistils), and their corollas are white. Therefore, it can sometimes be difficult to distinguish between them.

What is the difference between okra and tororo aoi?

However, there are significant differences between okra and hibiscus (Wu et al., 2007).

First, what is considered botanically important is the epicalyx lobe (also known as the secondary calyx or epicalyx), which is common to all plants in the Malvaceae family. The epicalyx lobe is a structure in which thin, leaf-like structures extend below the calyx, and as its alternative name, the secondary calyx, suggests, it appears as if there are two calyxes.

In okra, the calyx-like bracts are divided into 7 to 10 parts, which are thread-like to linear and 1 to 2.5 mm wide, whereas in tororo aoi (Abelmoschus manihot), they are divided into 4 or 5 parts, which are oblong-lanceolate and leaf-like in shape and 4 to 5 mm wide.

This method involves examining the underside of the flower, which might be difficult to notice, but it is the most reliable way to identify the plant. The calyx-like bracts remain attached from the bud to the immature fruit, so you will have plenty of opportunities to observe them.

However, these are not the only differences; there are also differences in the leaves and fruits.

Regarding the leaves, okra leaves are palmately divided into 3 to 7 lobes, each lobe is usually thick, and the leaf margins have slightly pointed serrations, whereas tororo aoi leaves are palmately divided into 5 to 9 lobes, each lobe is usually thin, and the leaf margins have blunt serrations.

Regarding the fruit, okra has a cylindrical to tower-shaped fruit, as seen on the dinner table, measuring 10-25 cm in length and 1.5-2 cm in width, with a beak-like tip. In contrast, tororo aoi has an oval to elliptical fruit, measuring 4-5 cm in length and 2.5-3 cm in width, with a rounded, blunt tip.

You should be able to distinguish them for sure by checking one of them.

What are the differences in how okra and tororo aoi (a type of okra) are used?

Okra is eaten as a vegetable even when the fruit is unripe (Singh et al, 2014). In the Eastern Mediterranean, including Iran, Egypt, Lebanon, Israel, Jordan, Iraq, Greece, and Turkey, it is widely used in rich stews made with vegetables and meat. In Indian cuisine, it is sautéed or added to gravy-based dishes and is very popular in South India. Since the end of the 20th century, it has become a popular vegetable in Japanese cuisine, eaten with soy sauce and bonito flakes, or deep-fried as tempura. It is also used in American Charleston gumbo, and in the American South, it is eaten breaded and deep-fried.

Globally, okra leaves can be cooked in the same way as beets and dandelion greens, and are sometimes eaten raw in salads. Okra seeds are also known to be a caffeine-free coffee substitute when roasted and ground.

On the other hand, the immature fruits of the tororo aoi plant are thick, short, and covered in stiff hairs, making them unsuitable for consumption. However, in Japan, the mucilage extracted from the roots is called "neri" (glue) and, along with that of the panicle hydrangea, has been used as an additive in the papermaking process of washi (Japanese paper) to uniformly disperse plant fibers such as mulberry and mitsumata (Machida, 2000). Nowadays, synthetic neri is often used.

What are the differences between *Broussonetia papyrifera* and *Broussonetia kozoa*? Do *Broussonetia papyrifera* flowers burst open? What is the history of *Broussonetia papyrifera*? Are its fruits edible?

Both *Broussonetia papyrifera* and *Broussonetia erythrorhizon* have been used as paper since ancient times, and *Broussonetia papyrifera* can still be found in familiar green spaces today. However, some literature suggests that the distinction between these two species is not very clear, and they have historically been confused with each other. However...

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What are the differences between Mitsumata and Ganpi? We'll explain how to distinguish between these similar species! Why is Mitsumata used as the raw material for Japanese banknotes? Do flowers require insects with long mouths to thrive?

Both Mitsumata and Ganpi belong to the Thymelaeaceae family and are used to make washi (Japanese paper). Their flowers are quite similar in shape. However, despite being in the same family, Mitsumata and Ganpi belong to different genera, and a closer examination of their flowering periods and inflorescence shapes reveals various differences. Ganpi was the first to be used for washi...

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In addition, as its alternative name "flower okra" suggests, the flowers are edible and used in salads, blanched dishes, and tempura, and in the Philippines, the leaves are sometimes used in cooking and salads.

What is the structure of a flower?

Malvaceae plants all share a common feature: a column formed by the fusion of stamens and pistils. You can see this column protruding from the center in both okra and hibiscus.

Okra flowers from May to September, with solitary flowers borne in the leaf axils (Wu et al., 2007). The pedicels are (0.5–)1–2(–5) cm long and have sparse bristles. The calyx-like involucral bracts number 7–10(–12), are filiform, 5–18 mm long × 1–2.5 mm wide, and coarsely wrinkled. The sepals are 2–3 cm long and conical, densely covered with stellate hairs. The corolla is yellow or white with a dark purple center, 5–7 cm in diameter, and the petals are obtuse, 3.5–5 cm long × 3–4 cm wide. The filamentous tube is 2–2.5 cm long.

Abelmoschus manihot flowers from August to October. The flowers are solitary, growing in the leaf axils, and also form a broad-spreading raceme at the top of the stem. The petals are 1.5–4 cm long. The calyx-like involucral bracts are 4–5 lobed, ovate-lanceolate, 15–25 mm long and 4–5 mm wide, with sparsely distributed long spines. The sepals are glossy, 5-lobed, almost entirely longer than the calyx-like involucral bracts, and covered only with soft hairs, without bristles, and are deciduous. The corolla is yellow with a purple center and about 12 cm in diameter. The stamens are 1.5–2.5 cm long, and the anthers are almost sessile. The stigma is purplish-black and spatulate to disc-shaped.

While the colors and structures are mostly the same, there are differences in how the flowers are attached, as well as in the calyx-like bracts and sepals. The dark purple color in the center of the corolla is thought to function as a "nectar guide" to attract insects.

How did it pollinate? Did it love bees?

Regarding pollination methods, okra can self-pollinate, but it is known that self-pollination reduces seed yield and seed size. Globally, it is generally believed that a certain amount of insect pollination is necessary, although this may vary depending on the variety (Nandhini et al., 2018). The study found that cross-pollination could yield approximately 73–841 TP3T of seeds per fruit, which is a higher probability of obtaining seeds compared to the 571 TP3T of seeds per fruit obtained through self-pollination.

Because okra is an important crop, there has been much research on it, and it has been found that it is mainly pollinated by bees (Azo'o et al., 2011; 2012; Nandhini et al., 2018). In India, it has been found to be pollinated by the Oriental honeybee and the genus Eucara, and in Cameroon, it has been found to be pollinated by the genera Eucara, Eucara, Bumblebee, European honeybee, Eucara macrognatha, and Tetralonia fraterna (Azo'o et al., 2011; 2012). Another study in South India also found that honeybees are responsible for pollination (Nandhini et al., 2018). However, there have been no studies on okra in Japan, so it is unknown whether the situation is similar in Japan.

Like okra, tororo aoi (Abelmoschus manihot) can self-pollinate, but it can also be cross-pollinated, and seed yield is more stable with insect-mediated cross-pollination (Kuwata, 1962; Qian et al., 2023).

While there is a lack of research on the pollinating insects of Abelmoschus manihot, it is believed to be pollinated by honeybees, wasps, beetles, and some species of butterflies and moths (Tyagi, 2002), but there appear to be no definitive studies showing the proportions.

In addition, okra plants form extrafloral nectaries on their sepals, attracting ants. Several examples can be found in Japan by performing a Google image search. While some believe ants play a role in pollination (Nandhini et al., 2018), ants are generally considered to have little contribution to pollination. It is also possible that they play a role in preventing nectar robbing, but research on this is not yet advanced. Overseas, there are known cases of the highly aggressive red imported fire ant Solenopsis invicta visiting okra, suggesting that they may have a significant impact on other insects.

What is the structure of the fruit?

The fruit, common to all species in the genus Abelmoschus, is a capsule. A capsule is a type of dry fruit, consisting of multiple fused, sac-like pericarps.

Okra capsules are cylindrical to tower-shaped, 10–25 cm long and 1.5–2 cm wide, with a beak-like tip. The seeds are dark brown or gray, spherical to kidney-shaped, containing 5–15 seeds per capsule, (3–)4–5(–6) mm in diameter, streaked, and finely wart-covered.

The capsules of Abelmoschus manihot are ovate to elliptical, 4-5 cm long and 2.5-3 cm wide, and densely covered with downy hairs. The seeds are numerous, with several rows of hairs, and kidney-shaped.

The immature okra fruit commonly used contains a mucilage that holds moisture, which includes pectin and mucilage. This mucilage helps store water, reduces water diffusion within the plant, aids seed dispersal and germination, and acts as a membrane thickener and nutrient storage (Gerrano, 2018). This may be related to its ability to grow even in tropical climates.

What are the seed dispersal methods?

If left unharvested, the fruit ripens and splits along the ovary chamber, scattering the seeds (Rao, 1991). Gravity dispersal is certain, but whether wind dispersal occurs is unknown. However, it can be said that nowadays most are harvested and seeds dispersed by human hands.

References

Azo'o, ME, Fohouo, FNT, & Messi, J. 2011. Influence of the foraging activity of the entomofauna on okra (Abelmoschus esculentus) seed yield. International Journal of Agriculture and Biology 13(5): 761-765. https://www.researchgate.net/publication/289381083

Azo'o, ME, Fohouo, FNT, & Messi, J. 2012. The importance of a single floral visit of Eucara macrognatha and Tetralonia fraterna (Hymenoptera: Apidae) in the pollination and the yields of Abelmoschus esculentus in Maroua, Cameroon. African Journal of Agricultural Research 7(18): 2853-2857. http://doi.org/10.5897/AJAR12.359, https://academicjournals.org/journal/AJAR/article-full-text-pdf/B2E531436937

Benchasri, S. 2012. Okra (Abelmoschus esculentus (L.) Moench) as a valuable vegetable of the world. Ratarstvo i povrtarstvo 49(1): 105-112. https://doi.org/10.5937/ratpov49-1172

Gerrano, AS 2018. Agronomic performance, nutritional phenotyping and trait associations of Okra (Abelmoschus esculentus) Genotypes in South Africa. In: O. Grillo (Ed.), Rediscovery of Landraces as a Resource for the Future (pp. 69-96). Intechopen. ISBN: 9781789237245, https://doi.org/10.5772/intechopen.70813

Kuwata, Akira. 1962. A study on the formation and drop of capsules in Abelmoschus manihot—particularly in relation to growth stages and environmental conditions. Journal of the Crop Science Society of Japan 30(3): 211-214. https://doi.org/10.1626/jcs.30.211

Masuda, K. 2009. Do you know about Tororo Aoi? Gakuen 828: 100-105. ISSN: 1348-0103, http://id.nii.ac.jp/1203/00004689/

Machida, Seiji. 2000. A Guide to Washi Paper: Its History and Chemistry. Tankosha, Kyoto. 298pp. ISBN: 9784473017390, https://cp.cm.kyushu-u.ac.jp/archive/Tips/japanese/washi/washi(5+6).pdf

Mohammed, W., Amelework, B., & Shimelis, H. 2020. Simple sequence repeat markers revealed genetic divergence and population structure of okra [' Abelmoschus esculentus '] collections of diverse geographic origin. Australian Journal of Crop Science 14(7): 1032-1041. https://search.informit.org/doi/abs/10.3316/informit.794714875294279

Nandhini, E., Padmini, K., Venugopalan, R., Anjanappa, M., & Lingaiah, HB 2018. Flower-visiting insect pollinators of okra [ Abelmoschus esculentus (L.) Moench] in Bengaluru region. Journal of Pharmacognosy and Phytochemistry 7(2): 1406-1408. ISSN: 2349-8234, https://www.phytojournal.com/archives?year=2018&vol=7&issue=2&part=T&ArticleId=3548

Qian, W., Hu, Y., Lin, X., Yu, D., Jia, S., Ye, Y., … & Gao, S. 2023. Phenological Growth Stages of Abelmoschus manihot: Codification and Description According to the BBCH Scale. Agronomy 13(5): 1328. https://doi.org/10.3390/agronomy13051328

Rao, LJ 1991. Induced mutations recovered in M ₂ and subsequent generations in three varieties of okra (Abelmoschus esculentus (L.) Moench). In: Horticulture: New Technologies and Applications (pp. 83-86). Kluwer Academic Pub, Dordrecht. ISBN: 9780792312796, https://doi.org/10.1007/978-94-011-3176-6_15

Singh, P., Chauhan, V., Tiwari, BK, Chauhan, SS, Simon, S., Bilal, S., & Abidi, AB 2014. An overview on okra (Abelmoschus esculentus) and it's importance as a nutritive vegetable in the world. International Journal of Pharmacy and Biological Sciences 4(2): 227-233. ISSN: 2321-3272, https://ijpbs.com/ijpbsadmin/upload/ijpbs_53df5a2907b19.pdf

Tyagi, AP 2002. Cytogenetics and Reproductive Biology of some BELE (Abelmoschus manihot Linn., Medic Sub-Species manihot) Cultivars. The South Pacific Journal of Natural and Applied Sciences 20(1): 4-8. https://doi.org/10.1071/SP02002

Wu, ZY, Raven, PH, & Hong, DY (Eds.). 2007. Flora of China (Vol. 12 Hippocastanaceae through Theaceae). Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis. ISBN: 9781930723641

The family Pontederiaceae consists of emergent, submerged, or floating aquatic plants, which are annual or perennial. The leaves are opposite, linear, or with clearly separated petioles and blades, and the blades are linear, orbicular, or scaly, with entire margins. The flowers are terminal, arranged in conical, umbel, or spike inflorescences, or borne in pairs or singly. The flowers are bisexual, bilaterally symmetrical or nearly radially symmetrical. The perianth segments are usually 6 in number, nearly free or tubular at the base, petal-like, and wilt quickly. The stamens are homomorphous or dimorphic, 6, 4, 3, or 1. The pistil has a superior ovary, 3-chambered, sometimes 1-chambered. The fruit is a capsule or a nutlet (pseudocarp) enclosed at the base of the perianth segments. There are many or 1 seed. There are 9 genera and about 33 species found in tropical to temperate regions worldwide. Two species of the genus Monochoria are native to Japan, while one species each of the genera Hyacinth, Monochoria, and Pontederia have become naturalized.

This article provides a comprehensive, field guide-style introduction to plants belonging to the Pontederiaceae family.

The basic information is based on the Kanagawa Prefecture Flora Survey Association (2018). Photos are replaced as better ones become available. While the identification is done by the author, please note that misidentifications may be corrected without notice.

No. 0636 Water Hyacinth (Eichhornia crassipes)

Also known as water hyacinth, water hyacinth, and water sedge. It is a perennial plant, but can be grown annually in colder climates. The basal leaves grow in clumps. The leaf blades are ovate, 4-10 cm long. The flower stalks are about 20 cm tall and bloom from August to October. The flowers are 3 cm in diameter, and the perianth segments are pale purple. The entire inflorescence blooms simultaneously, then curls back and sinks into the water the following day. Native to tropical America, it has naturalized in Honshu (west of the Kanto region), Shikoku, Kyushu, and the Ryukyu Islands. It overwinters and naturalizes in riverbanks and ponds in various locations. It has been designated as an alien species that causes damage to ecosystems by the Ministry of the Environment (a species of concern before March 2017), and has also been selected as one of the "World's 100 Worst Invasive Alien Species" by the International Union for Conservation of Nature (IUCN) and one of the "Japan's 100 Worst Invasive Alien Species" by the Ecological Society of Japan.

References

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Aucuba japonica is distributed in evergreen broad-leaved forests of East Asia and is a very common plant in Japan , even in urban areas, where it's rare to go a day without seeing it. Several varieties of Aucuba japonica are known, and they are often divided into Aucuba japonica (in the narrow sense), Aucuba japonica var. These Aucuba species bear small, unassuming purplish-brown flowers. They are so inconspicuous that most insects would likely ignore them, but research has shown that these flowers are exclusively visited by fungus gnats. This is thought to be a clever pollination strategy within the forest. Furthermore, their conspicuous red fruits are frequently eaten by bulbuls for some reason, thus dispersing their seeds. This article will explain the classification, evolution, pollination ecology, and seed dispersal of Aucuba species.

Evergreen trees can be found everywhere, from forests to urban areas.

Aucuba japonica var. japonica (in the narrow sense) is an evergreen shrub distributed in Honshu, Japan (Tohoku to eastern Shikoku), and Korea, growing in evergreen broad-leaved forests, bright deciduous forests, and plantations (Mogi et al., 2000). It is abundant and frequently encountered when observing in evergreen broad-leaved forests. It is tolerant of both heat and cold, can grow in shade, and is often cultivated as a garden tree and park tree due to its red fruits and dark green leaves. Some varieties, such as Aucuba japonica 'Variegata', have variegated leaves.

Aucuba japonica var. ovoidea, also known as Southern Aucuba, is an evergreen shrub distributed in Honshu (west of the Chugoku and Shikoku regions), Kyushu, and Okinawa in Japan, as well as in Taiwan (Oi, 2004; Tsusaka et al., 2011). It grows in forests as a substitute for Aucuba japonica (in the narrow sense) and is cultivated as a garden tree and park tree.

Aucuba japonica var. borealis, also known as Hime-aoki, is an evergreen shrub distributed in southwestern Hokkaido and the snowy regions along the Sea of Japan on Honshu in Japan. It grows in slightly shaded areas within and at the edges of mountain forests.

All of these species belong to the genus Aucuba in the family Aucubaceae, and are included within the broad category of Aucuba japonica. Including all varieties, they are distributed very widely in Japan, from southwestern Hokkaido to Okinawa. They have large, glossy, oval leaves that grow opposite each other. There is considerable variation in leaf size, width, and serration size, but they are generally easily distinguished from other species by the presence of large, sparsely spaced serrations. The thicker branches are green. They are dioecious, meaning that male plants bear male flowers and female plants bear female flowers.

However, some people may find it difficult to distinguish between varieties based solely on their names.

What are the differences between Aucuba japonica, Aucuba japonica var. japonica, and Aucuba japonica var. japonica?

To distinguish between these three varieties, it is necessary to examine their distribution and morphology.

As mentioned above, Aucuba japonica is found in Honshu, Japan (from Tohoku to eastern Shikoku); and in Korea; Aucuba japonica var. nagoshu is found in Honshu, Japan (west of the Chugoku and Shikoku regions), Kyushu, and Okinawa; and Aucuba japonica var. japonica is found in southwestern Hokkaido and the snowy regions along the Sea of Japan on Honshu. These species are basically mutually exclusive, so they can be distinguished to some extent just by the regions where they are found.

However, the distribution of Aucuba japonica and Aucuba japonica var. serrata overlaps in the Chugoku and Shikoku regions, and the same is true for Aucuba japonica var. japonica var. japonica. It is probably not a good idea to distinguish them while ignoring their morphology.

Firstly, *Aucuba japonica* is a small plant, reaching a height of about 1 meter, with leaves less than 15 cm long, creeping branches, and short hairs on its young branches and leaves. In contrast, *Aucuba japonica* and *Aucuba japonica var. serrata* are larger plants, reaching a height of 2 to 3 meters, with leaves 8 to 25 cm long, upright branches, and no hairs on their young branches or leaves (Hayashi, 2014).

Regarding Aucuba japonica and Aucuba japonica var. japonica, Aucuba japonica tends to have relatively small leaves with sharp serrations, while Aucuba japonica var. japonica tends to have relatively large leaves with blunt serrations.

Let's make a distinction based on all of the above.

However, recent research suggests that Aucuba japonica var. nangokuensis is indistinguishable from Aucuba japonica (Ohashi et al., 2017). This is likely because Aucuba japonica (in the broad sense) exhibits considerable variation in leaf shape. It remains to be seen whether it will be treated as a separate variety in the future, or whether such a distinction will cease to be made, but observing it with the understanding that there are differences might reveal various insights.

What are the different varieties of Aucuba japonica?

While there are only three officially recognized varieties of Aucuba japonica, there are several populations that are treated as "cultivars" due to subtle differences, even though these differences are not significant enough to warrant the designation of "varieties."

The Japanese laurel (Aucuba japonica var. japonica) includes several wild varieties: white-fruited Aucuba japonica f. leucocarpa, yellow-fruited Aucuba japonica f. luteocarpa, and green-petaled Aucuba japonica f. viridiflora. Cultivated varieties include 'Variegata' with variegated leaves, 'Luteo-marginata' with white variegation on the leaf margins, and 'Picturata' with variegation in the center of the leaves.

Wild varieties of Aucuba japonica var. borealis include Aucuba japonica f. albivariegata, which has variegated leaves, and Aucuba japonica f. albivariegata, which (although direct confirmation is not possible due to the scarcity of literature) has uneven leaves.

Why did Aucuba japonica and Aucuba japonica diverge into two varieties?

Hime-aoki is a variety found only in Japan. This means it branched off from Aucuba japonica (in the narrow sense) within Japan, but why did this branching occur?

The main reason for this is that *Aucuba japonica* is distributed along the Sea of Japan coast. Let's start by understanding Japan's climate.

The Japanese archipelago stretches long and narrow from north to south, with the Eurasian continent and the Sea of Japan to the northwest and the Pacific Ocean to the southeast. As a result, the Sea of Japan side and the Pacific Ocean side of Honshu experience vastly different weather conditions due to the seasonal winds of summer and winter.

Japanese monsoon winds are generated by the difference in specific heat (the amount of heat required to raise the temperature of a substance by 1 degree Celsius per gram) between the Eurasian continent and the Pacific Ocean.

The concept of "specific heat" is a little difficult to understand, but essentially it is a value that indicates the difference in how easily heat is transferred. Comparing the specific heat of the Eurasian continent and the Sea of Japan, heat conduction occurs easily in the solid, dense Eurasian continent, so it heats up and cools down quickly (low specific heat), while heat conduction is difficult in the liquid, less dense Pacific Ocean, so it heats up and cools down slowly (high specific heat). In other words, continents are more susceptible to seasonal changes than oceans.

Therefore, the response to the sun's heat (sunlight) differs. In summer, the sunlight is strong, and the air over the Eurasian continent is warmed, becoming less dense and lighter, which creates updrafts and low pressure systems. On the other hand, the Pacific Ocean is less affected by sunlight, but it becomes relatively colder, and the air over the Pacific cools and becomes denser, creating downdrafts and high pressure systems.

In this situation, a circulation of air flows from the Pacific Ocean to the Eurasian continent near the ground, and from the Eurasian continent to the Pacific Ocean in the upper atmosphere, resulting in the generation of a "southeasterly monsoon" from the Pacific Ocean to the Eurasian continent near the ground.

Conversely, in winter, sunlight weakens, but the air over the Eurasian continent cools, becomes denser and heavier, creating downdrafts and high pressure systems. On the other hand, the Pacific Ocean is less affected by sunlight but becomes relatively warmer, and the air over the Pacific warms up, becoming less dense, creating updrafts and low pressure systems.

In this scenario, air circulation occurs from the Eurasian continent to the Pacific Ocean near the ground, and from the Pacific Ocean to the Eurasian continent in the upper atmosphere, resulting in the generation of a "northwest monsoon" from the Pacific Ocean to the Eurasian continent near the ground.

We now understand the mechanism of seasonal wind generation, but how are the climates of the Japanese archipelago affected by these seasonal winds?

The Japanese archipelago is divided into two sides by the Japanese Alps, which form the backbone of the mountain range, separating the Sea of Japan side from the Pacific Ocean side.

In summer, southeasterly monsoon winds blow from the Pacific Ocean, carrying moisture from the sea. On the Pacific side, these winds collide with the Japanese Alps, removing moisture and resulting in heavy rainfall. However, on the Sea of Japan side, the air flows after crossing the Japanese Alps, resulting in drier air, more sunny days, and very little rainfall.

On the other hand, in winter, cold northwesterly monsoon winds blow from the Eurasian continent, but they also draw in the warm moisture from the Sea of Japan. On the Sea of Japan side, from the plains to the mountainous areas north of Honshu, it brings heavy snowfall rather than rainfall, as is typical in winter. The snow that accumulates from December to February often remains until March to May because there are few sunny days. In contrast, on the Pacific side, dry air flows after crossing the Japanese Alps, resulting in many sunny days and very little snowfall.

Thus, the Japanese archipelago experiences significant differences in rainfall and snowfall between summer and winter, with the Japanese Alps as the dividing line. Of these, plants are most greatly affected by the amount of snowfall in winter.

Japanese laurel (Aucuba japonica) evolved through various adaptations to cope with the reduced sunlight and decreased photosynthesis caused by heavy snowfall in winter on the Sea of Japan side, as well as to withstand the weight of the snow. In particular, it has been found that the annual photosynthetic production decreases by more than 301 TP3 T on the Sea of Japan side.

Plants that have undergone such adaptations are known as "Sea of Japan elements," and many others are known, including Camellia japonica (corresponding to Camellia japonica on the Pacific side), Daphniphyllum macropodum (corresponding to Daphniphyllum macropodum on the Pacific side), Skimmia japonica (corresponding to Skimmia japonica on the Pacific side), Ilex crenata (corresponding to Ilex rotunda on the Pacific side), Ilex crenata (corresponding to Ilex crenata on the Pacific side), and Ilex integra (corresponding to Ilex integra on the Pacific side) (Kume, 1996; 1998).

How did Japanese laurel adapt to the heavy snowfall areas on the Sea of Japan side?

Specifically, how does *Aucuba japonica* adapt to the climate of the snowy regions on the Sea of Japan side?

Morphologically, as mentioned above, the plant body is small and its branches creep along the ground. This could simply be due to a low rate of photosynthesis and a lack of resources to strengthen the plant, but it is also possible that this prevents the branches from breaking under the weight of the snow (Sakai, 1976).

Furthermore, it has been found that because branches and trunks break and they cannot grow tall, they allocate resources to increasing the amount of leaves per stem (Kume, 1996). This certainly allows them to increase photosynthesis even in low sunlight, and can be said to be a win-win adaptation.

Although I couldn't find any literature that directly mentions the reason why short hairs grow on young branches and leaves, it is thought that they serve to prevent snow from directly contacting the plant body and to provide insulation.

Furthermore, in terms of reproduction, the plant not only reproduces through seed propagation, a type of sexual reproduction through insect pollination, but also through vegetative reproduction, a type of asexual reproduction through branching of rhizomes and the development of non-adoptive roots (Sakai, 1976; Higashi & Ino, 2003). This is thought to serve as a safety net in case photosynthesis is insufficient and nutrients prevent the plant from producing flowers or seeds.

On the other hand, no significant physiological differences have been observed between Aucuba japonica and Aucuba japonica var. japonica (Kume, 1996). This is in contrast to the relationship between Camellia japonica and Camellia japonica var. japonica, and is thought to be because the ancestors of Aucuba japonica originally developed adaptations for cold environments.

By the way, after hearing all this, you might feel that living in the snow has only disadvantages. While there are certainly such aspects, it's not entirely accurate to say so. Several advantages have also been pointed out (Kume, 1998).

For example, the temperature near the ground surface beneath the snow remains at 0°C, which prevents freezing and provides insulation. It's similar to a snow hut.

Furthermore, humidity is maintained at nearly 100% under and within snow cover, providing a moisturizing effect.

And because there is a large amount of snowmelt water, they never have to worry about water shortages.

Why did Aucuba japonica and Aucuba japonica diverge into two varieties?

On the other hand, for what reason did Aucuba japonica and Aucuba japonica 'Nangoku' diverge?

Studies examining chromosomes have revealed that there is a difference in chromosome number between Aucuba japonica and Aucuba japonica var. serrata. According to this study, Aucuba japonica (and Aucuba japonica var. serrata) is tetraploid with a chromosome number of 2n=32, while Aucuba japonica var. serrata is diploid with a chromosome number of 2n=16 (Tsusaka et al., 2011).

This is thought to be the reason for the difference between Aucuba japonica and Aucuba japonica var. serrata. So why did the number of chromosomes change between Aucuba japonica and Aucuba japonica var. serrata?

The reason is not fully understood, but it is thought that the ancestors of Aucuba japonica once reduced their distribution within the Japanese archipelago during the last glacial period.

During the last glacial period, when the Earth cooled, the ancestors of Aucuba japonica were forced to move to very limited areas within the Japanese archipelago, known as refuges. At this time, the number of chromosomes changed due to some genetic cause, such as a "bottleneck effect" or mutation.

After the last glacial period, the diploid Aucuba japonica and tetraploid Aucuba japonica that remained in the refuge likely expanded their distribution again in the Chugoku and Shikoku regions, with Aucuba japonica spreading from the west and Aucuba japonica from the east, respectively, due to the subsequent warming of the climate.

Furthermore, it is believed that current climatic factors also play a role in the areas where the distributions overlap. It is thought that in warmer regions such as the Sea of Japan side and the Setouchi region, Aucuba japonica spread slightly eastward, while in cooler regions such as the Chugoku Mountains, Aucuba japonica spread slightly westward, thus forming the current distribution.

What is the structure of the Aucuba flower?

Aucuba japonica (in the narrow sense) blooms in spring, from March to April. It produces a conical inflorescence bearing numerous small, purplish-brown flowers. Both male and female flowers are about 1 cm in diameter and have four petals. The petals are oblong-ovate in shape with sharply pointed tips. Male flowers have four stamens with pale yellow anthers, while female flowers have a pistil in the center and no stamens.

The flowering period of Aucuba japonica is from March to May, and otherwise it is almost the same as Aucuba japonica (in the narrow sense). Aucuba japonica also has almost the same characteristics as Aucuba japonica (in the narrow sense).

It appears that the flowers have not evolved significantly from one variety to the next.

Aucuba flowers are only for tiny flies!?

As you can see, the flowers of the Aucuba japonica are purplish-brown and not particularly conspicuous, at least to humans. Furthermore, because they commonly grow in forests, they are even harder to spot. Of course, we can't say for sure without imagining the feelings and sensations of the insects that visit the flowers, but it seems that they are also quite inconspicuous to insects. Why is this the case?

A study that observed insects visiting for 33 hours found that while various types of insects such as flies, beetles, moths, bees, and caddisflies were observed, 88.6% were flies (Mochizuki & Kawakita, 2018). Furthermore, it was found that 68.6% of these were very small and inconspicuous flies belonging to the families Mycetophilidae and Sciaridae.

They are known to be abundant in forests because their larval stage involves feeding on mold and fungal mycelium. Therefore, it is reasonable to assume that they rely heavily on flies for pollination.

Research has revealed that many plant species besides Aucuba japonica rely on fungus gnats and black fungus gnats for pollination. Flowers of plants pollinated by these flies are generally flat, have short stamens, and are dark red in color. These plants all grow in forests, in environments with little light. Therefore, they cannot attract ordinary insects by using color to stand out, as is common with ordinary flowers. On the other hand, color vision is not currently known to be developed in fungus gnats. Therefore, they haven't evolved to make their flowers more conspicuous. Wouldn't it be considered very rational for these plants to rely on insects that are abundant in the forest to carry their pollen, without relying on color vision?

How do flowers attract flies? Why are they purplish-brown?

So, if that's the case, how do you attract fungus gnats?

While it's not fully understood, scent is thought to be important. Similarly, in the Euonymus family, which has similar flowers and relies on fungus gnats and black fungus gnats for pollination, they produce a very rare plant-derived scent substance called "acetoin." It's still unclear whether fungus gnats are truly attracted to this substance, but it seems highly likely that Aucuba japonica also attracts them with a scent substance.

However, if the goal is to attract insects with scent, wouldn't any dark color work, not just dark red? Upon further investigation, it has been discovered that dark red flowers have a structure that does not reflect ultraviolet light, which insects should be able to see. This makes them the least conspicuous color for insects. In other words, it is currently believed that dark red is the optimal color for keeping away unwanted insects other than fungus gnats.

It should be noted that no research has been conducted on Aucuba japonica var. japonica or Aucuba japonica var.

For some reason, only brown-eared bulbuls were eating the red berries of the Aucuba japonica plant!?

The fruits of Aucuba japonica are all drupe. They are oblong or ovate-oblong, 1.5-2 cm long, and ripen red from December to May. The surface is glossy, and there is a single seed inside. The seed is oblong, 1.3-1.5 cm long and 7-8 mm wide, with a groove in the center. The fruits remain on the branches for a long period, and flowers and fruits are often seen together.

What animals eat these very conspicuous red fruits and disperse their seeds?

Of the three varieties, *Aucuba japonica* has been studied in detail. There are two studies, both of which point out that it is mainly eaten by the brown-eared bulbul * Hypsipetes amaurotis * and the field mouse * Apodemus speciosus* (Yamaguchi and Hayashida, 2009; Nakagawa and Kitamura, 2017).

In particular, a study conducted at the Ishikawa Prefectural Forestry Experiment Station counted the number of fruits on 980 individual Aucuba japonica trees and recorded the number of fruits remaining on the trees once a week using an automatic camera (Nakagawa and Kitamura, 2017). The results showed that 45.21 TP3T of the fruits were eaten by bulbuls and 27.11 TP3T by field mice, with these two species accounting for 72.31 TP3T, while the remainder were consumed only slightly by numerous birds and mammals.

However, since the Japanese field mouse (Acer palmatum) was found to be damaging not only the fruit but also the seeds of Aucuba japonica (Yamaguchi and Hayashida, 2009), rodents are not considered to be effective seed dispersers of Aucuba japonica (Nakagawa and Kitamura, 2017). Therefore, it can be said that the brown-eared bulbul is the main seed disperser.

In late April, as the cherry blossoms finish blooming, it has been observed that brown-eared bulbuls, which previously fed on cherry blossom nectar, switch their diet to the fruits of the Japanese laurel.

But why is it only the brown-eared bulbul that eats the fruit of the Japanese laurel?

Unfortunately, the reason for this is not entirely clear. However, given that the fruits of Aucuba species are as wide as 8 mm, it is likely that only birds with large mouths would be able to eat them. It has also been pointed out that the pulp layer of Aucuba species is extremely thin compared to the seeds (Ueda, 1999), which makes it an unsuitable food source and suggests that the fruit may be a form of mimicry. Nevertheless, it is possible that only a limited number of species prefer to eat them as a food source.

Although not reflected in this study, the authors of this paper have observed thrushes such as the Blackbird, Pale Thrush, and Red-flanked Thrush feeding on the fruits of Aucuba japonica in the same study area. For some reason, this was not observed in this photographic experiment, but it is possible that birds other than the Brown-eared Bulbul also contribute to the dispersal of Aucuba japonica seeds to some extent.

On the other hand, you might be wondering what the situation is like with Aucuba japonica (in the narrow sense), which is widely found on Honshu.

Unfortunately, there are no studies yet that have examined the proportion of animals that ate the fruit, but there are records of the fruit being eaten by bulbuls, azure-winged magpies, thrushes, pale thrushes, starlings, pheasants, copper pheasants, and Japanese grosbeaks (Nakagawa and Kitamura, 2017). In a previous study in which bulbuls were experimentally fed the fruit, the seeds showed a germination rate as high as that of seeds from which the pulp had been artificially removed. Furthermore, since Aucuba japonica seeds have been found in the droppings of bulbuls captured in the wild, it is highly likely that bulbuls are indeed the main carriers of the seeds.

References

Higashi, Naoyoshi and Ino, Yoshio. 2003. Analysis of the clonal structure of *Aucuba japonica* populations using the AFLP method. Abstracts of the Annual Meeting of the Ecological Society of Japan 50: 259. https://doi.org/10.14848/esj.ESJ50.0_259_4

Hayashi, Masayuki. 2014. 1100 Tree Leaves Identified Through Real-Life Scans. Yama-kei Publishers, Tokyo. 759pp. ISBN: 9784635070324

Kume, Atsushi. 1996. Physiological and ecological studies on the adaptation of evergreen shrubs to heavy snow environments. [Doctoral dissertation, Waseda University]. https://doi.org/10.11501/3123934, http://www.forest.kyushu-u.ac.jp/staff/kume/KumeDoc1996rev.pdf

Kume, Atsushi. 1998. On the effects of heavy snowfall on flora. Waseda Biology 31: 19-24. ISSN: 0511-1978, http://www.forest.kyushu-u.ac.jp/staff/kume/TaniSnow.pdf

Ohashi, Hiroyoshi; Kadota, Yuichi; Murata, Hitoshi; Yonekura, Koji; and Kihara, Hiroshi. 2017. Wild Plants of Japan (Revised New Edition, Vol. 4 Malvaceae to Apocynaceae). Heibonsha, Tokyo. 348pp. ISBN: 9784582535341

Oi, Tetsuo. 2004. Distribution changes of widely distributed species in the Japanese archipelago as seen from chloroplast DNA polymorphisms. Koishikawa Botanical Garden Lecture Series Newsletter 26: 8-10.

Sakai, Akira. 1976. Adaptation of plants to snow cover. Low Temperature Science, Biology Edition 34: 47-76. ISSN: 0439-3546, https://hdl.handle.net/2115/17828

Tsusaka, Machiko, Yamamoto, Nobuko, and Ikeda, Hiroshi. 2011. A cytogeographical study of Aucuba japonica (Aucubaceae)—particularly regarding its distribution near boundaries. Naturalistae 15: 13-22. ISSN: 1349-7731, https://ous.repo.nii.ac.jp/records/3389

Mochizuki, K., & Kawakita, A. 2018. Pollination by fungus gnats and associated floral characteristics in five families of the Japanese flora. Annals of Botany 121(4): 651-663. ISSN: 0305-7364, https://doi.org/10.1093/aob/mcx196

Mogi, Toru; Ota, Kazuo; Katsuyama, Teruo; Takahashi, Hideo; Shirokawa, Shiro; Yoshiyama, Hiroshi; Ishii, Hidemi; Sakio, Hitoshi; and Nakagawa, Shigetoshi. 2000. Flowers Blooming on Trees: Polypetalous Flowers (Vol. 2, 2nd edition). Yama-kei Publishers, Tokyo. 719pp. ISBN: 9784635070041

Nakagawa, Koyo & Kitamura, Shunpei. 2017. The quantitatively effective seed disperser of the evergreen shrub *Aucuba japonica* in cedar forests of central Japan is the brown-eared bulbul. Bird Research 13: A55-A68. https://doi.org/10.11211/birdresearch.13.A55

Ueda, Keisuke. 1999. Unexpected Birds' Unexpected Preferences: Who Eats the Inconspicuous "Dry Fruit"?. In: Ueda, Keisuke (Ed.), Seed Dispersal: The Evolution of Mutual Aid Vol. 1: Seeds Carried by Birds (pp. 64-75). Tsukiji Shokan. ISBN: 9784806711926

Yamaguchi, Yoshihiko and Hayashida, Kosuke. 2009. Effects of gall formation by the gall midge Aucuba japonica on seedling regeneration. Journal of the Japanese Forestry Society 91(3): 159-167. https://doi.org/10.4005/jjfs.91.159