Isunoki - Isunoki

An evergreen tree of the Hamamelidaceae (APG classification: Hamamelidaceae) that can reach a height of 20 meters and a diameter of 1 meter, and is a typical component of evergreen broadleaf forests in southern Kyushu. The bark is gray-brown. The leaves are thick and hard, elliptical, without sawtooth, and often develop galls. Flowers appear in March and April in panicles that emerge from the leaf axils, are red, and have no petals. One inflorescence contains a mixture of male and bisexual flowers. The fruit is a capsule with two projections at the tip, densely covered with yellowish-brown stellate hairs, and shallowly bisected to release the seeds. It is distributed from the Tokai region of Honshu westward to Shikoku, Kyushu, Okinawa, and further to Jeju Island, Taiwan, and China. Its wood is the heaviest and hardest of all useful tree species in Japan, and is used for a variety of purposes, including abacus beads, combs, alcove pillars, and lintels. It is also called Hyon-noki because of the sound it makes when blowing on its galls. The Distylium genus is endemic to eastern and southern Asia, and consists of 18 species.

[Yuichi Kadota May 19, 2020]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

マンサク科（APG分類：マンサク科）の常緑高木で、高さ20メートル、直径1メートルに達し、南九州の常緑広葉樹林の代表的な構成樹種。樹皮は灰褐色。葉は厚くて硬く、楕円(だえん)形、鋸歯(きょし)はなく、よく虫こぶができる。花は3～4月、葉腋(ようえき)から出た円錐(えんすい)花序につき、紅色、花弁はない。一つの花序に雄花と両性花が混在する。果実は蒴果(さくか)、先端に2本の突起があり、黄褐色の星状毛が密生し、浅く2裂して種子を放出する。本州の東海地方以西から四国、九州、沖縄、さらに済州島、台湾、中国に分布する。材は日本産有用樹種のなかでももっとも重くかつ硬く、そろばん玉、櫛(くし)、床柱、鴨居(かもい)などさまざまな用途に賞用される。虫こぶを吹くと鳴る音からヒョンノキともいう。イスノキ属はアジア東部から南部に固有な属で、18種からなる。

［門田裕一　2020年5月19日］

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