Bidens dangusa - Bidens dangusa

An annual plant of the Asteraceae family. The stem is erect and 30-150 cm tall. The leaves are opposite at the bottom and alternate at the top. From September to November, the heads of small yellow female and bisexual flowers grow at the ends of the twigs. The female flowers are ray-shaped and do not bear fruit, while the bisexual flowers are tubular. The achene is linear and tetragonal with three or four awns at the end. These awns have small, inverted thorns that make them difficult to remove from clothing. It grows in slightly damp grasslands and on the edges of ditches, and is found in the Chubu region of Honshu and southward, and is also widely distributed in the tropical and subtropical regions of Asia, Africa, and Europe. Its name comes from the fact that its leaves resemble those of China tree. A closely related species, China tree (B. bipinnata L.), which has finely cut leaves, is not as common as China tree.

[Hiroyuki Koyama]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

キク科の一年草。茎は直立し、高さ30～150センチメートル。葉は下部では対生し、上部では互生する。9～11月、小枝の先に雌性と両性の黄色の小花からなる頭花をつける。雌花は舌状花で結実せず、両性花は管状花で結実する。痩果(そうか)は線形で扁四稜(へんしりょう)形、先端に3、4個の芒(のぎ)がある。この芒には逆向きの小さい刺(とげ)があって、衣服につくと離れにくい。やや湿った草地や溝の縁に生え、本州中部地方以南に生育し、さらにアジア、アフリカ、ヨーロッパの熱帯、亜熱帯に広く分布する。名は、葉がセンダンに似ていることによる。近縁種で、葉が細かく切れ込んだコバノセンダングサB. bipinnata L.はセンダングサほど多くない。

［小山博滋］

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