Water chickweed - Water chickweed

An annual plant of the family Lythrum mallid (APG classification: Lythrum mallid). The whole plant is small and soft, and when dry, it takes on a reddish hue. The stem spreads horizontally, is 3-10 cm long, and is highly branched. The leaves are opposite, broadly lanceolate or narrowly ovate, rounded at the tip, narrow at the base, and hairless. From June to August, pale pink florets grow singly in the leaf axils. There are three sepals, which are fused at the base. There are three petals, which are slightly longer than the sepals. There are three short styles that stand upright. The capsule is oblate and membranous. It grows in wetlands such as rice paddies, and is distributed from Honshu to Okinawa, as well as the Northern Hemisphere and South America.

The Elatinaceae family is a dicotyledonous polypetalous plant. It is an annual or perennial herb. The leaves are opposite or whorl-arranged with stipules. The flowers are small and bisexual. There are 3-5 sepals and petals that are separate. There are either the same number of stamens as the petals or twice as many. There are about 40 species in 2 genera worldwide, and 2 genera and 2 species are found in Japan.

[Junko Kobayashi, June 23, 2020]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

ミゾハコベ科（APG分類：ミゾハコベ科）の一年草。全草小形で柔らかく、乾くと紅色を帯びる。茎は横にはい、長さ3～10センチメートルで分枝が多い。葉は対生し、広披針(こうひしん)形または狭卵形で先は丸く、基部は狭まり、毛はない。6～8月、葉腋(ようえき)に淡紅色の小花を単生する。萼片(がくへん)は3枚、基部は癒合する。花弁は3枚、萼片よりやや長い。花柱は3本で短く、直立する。蒴果(さくか)は扁球(へんきゅう)形で膜質。水田などの湿地に生え、本州から沖縄、および北半球、南アメリカに分布する。

　ミゾハコベ科Elatinaceaeは双子葉植物離弁花類。一年草または多年草。葉は対生か輪生で托(たく)葉がある。花は小形で両性。萼片と花弁は3～5枚で離生する。雄しべは花弁と同数か2倍数。世界に2属約40種あり、日本に2属2種分布する。

［小林純子　2020年6月23日］

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