Yamaha box - Yamaha box

A perennial plant of the Asteraceae family. The stem is 30-70 cm tall and densely covered with white fluff. The leaves are numerous and alternate, narrowly lanceolate, 6-9 cm long, somewhat thick, and have three veins. The upper surface is green, while the underside is densely covered with white or light brown fluff, with rolled edges. Dioecious. In August and September, the corymbs form at the ends of the branches and produce numerous flower heads. The hermaphrodite flowers are tubular with five teeth at the end, while the female flowers are thread-like and shorter than the style. The involucre is spherical and 5 mm long, the involucre pieces are dry membranous, white on the upper half and dark brown on the lower half, densely covered with fine hairs. It is distributed from the Himalayas to North America, but in Japan it grows in sunny grasslands in the mountains of Ishikawa Prefecture, Honshu north of Nagano Prefecture, and Hokkaido, but not in western Japan.

The subspecies Hosobanoyamahako is found in Honshu, west of Fukui and Aichi prefectures, and in Kyushu. The entire plant is smaller than Yamahako, with narrow leaves measuring 2-6 mm wide and about 5 cm long. The subspecies Kawarahako, which is commonly found in sandy riverbeds throughout Japan, has linear leaves that are even smaller, measuring about 1.5 mm wide.

[Hiroyuki Koyama]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

キク科の多年草。茎は高さ30～70センチメートル、白色の綿毛を密生する。葉は多数互生し、狭披針(きょうひしん)形で長さ6～9センチメートル、やや厚く、3脈がある。表面は緑色を呈し、裏面は白色または淡褐色の綿毛を密生し、縁(へり)は巻き込む。雌雄異株。8～9月、枝先に散房花序をつくり、多数の頭花をつける。両性花は筒状で先に5歯があり、雌性花は糸状で花柱より短い。総包は球形で長さ5ミリメートル、総包片は乾膜質で上半は白色、下半は暗褐色で細毛を密生する。ヒマラヤから北アメリカに分布するが、日本では石川県、長野県以北の本州、北海道の山地の日当りのよい草地に生育し、西日本にはない。

　福井県、愛知県以西の本州から九州には亜種のホソバノヤマハハコが分布する。全草がヤマハハコに比べて小さく、葉幅も2～6ミリメートルと狭く、長さも約5センチメートルと短い。日本各地の川原の砂地に多くみられる亜種カワラハハコの葉は線形で、幅は約1.5ミリメートルとさらに小さい。

［小山博滋］

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