Dicotyledonous, polypetalous. Herbaceous or shrub, mostly terrestrial but some aquatic. Leaves are opposite, alternate or whorled, without stipules, and submerged leaves are finely divided. Flowers are bisexual or unisexual, in panicles, and very small. Calyx encases ovary, forming a calyx tube, with 2-4 lobes at the end or no lobes. Petals are absent or 2-4, arranged in a slightly imbricate shape. Stamens are 2-8, anthers are attached to the base and split longitudinally. Ovary is inferior with 1-4 locules, ovules hang from the apex of the locus. Fruits are small nuts or drupes, winged, do not dehisce, and some produce drupes. Seeds contain a large amount of endosperm. They are widely distributed in the tropical and temperate zones of both the northern and southern hemispheres, with about 8 genera and 160 species in the world. In Japan, there are two genera: the small terrestrial herbaceous genus Haloragis and the weak aquatic herbaceous genus Myriophyllum . [Junko Kobayashi October 18, 2019] It is also classified as a Pterocallidae in the APG classification. [Editorial Department, October 18, 2019] Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend |
双子葉植物、離弁花類。草本または低木で、多くは陸生であるが水生のものもある。葉は対生、互生または輪生し托葉(たくよう)はなく、水中葉は細かく分裂する。花は両性または単性で円錐(えんすい)花序をなし、ごく小形。萼(がく)は子房を包んで萼筒(がくとう)をなし、先は2~4裂するか、または裂片がない。花弁はないか、または2~4枚あり、やや覆瓦(ふくが)状に並ぶ。雄しべは2~8本、葯(やく)は底着し縦裂する。子房は下位で1~4室、胚珠(はいしゅ)は室の頂端から下垂する。果実は小形で堅果または核果をつくり、翼があり裂開せず、分果をつくるものもある。種子には多量の胚乳をもつ。南北両半球の熱帯、温帯に広く分布し、世界に約8属160種がある。日本では陸生の小形の草本のアリノトウグサ属Haloragisと、水生の軟弱な草本のフサモ属Myriophyllumの2属が分布する。 [小林純子 2019年10月18日] APG分類でもアリノトウグサ科とされる。 [編集部 2019年10月18日] 出典 小学館 日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について 情報 | 凡例 |
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