Welwitschia mirabilis

Japanese: ウェルウィッチア（英語表記）Welwitschia mirabilis

A gymnosperm of the Welwitschia family. It grows naturally in the deserts of southwestern Africa. It was first discovered in 1860 by F. Welwitsch in Portuguese Angola, and in the same year by J.T. Baines in Damaraland, Namibia, and was named by J. Hooker. It is a very rare plant with one genus and one species, and its appearance is different from any other plant. Most of the stem is buried underground, and only the thick part of the inverted cone is exposed above ground. The top of the stem is about 1m in diameter, and has two huge belt-like leaves on the edge. The leaves grow larger every year, and can live for hundreds of years. When they get old, they split vertically and twist, spreading out on the ground, reaching a length of 3 to 3.5m. They are dioecious, and both have cone-shaped inflorescences at the top of the stem. The male flowers have two pairs of perianths, one inside and one outside, and six stamens inside, and the bases of the stamens are fused together to form a tube. There is a single degenerated ovule in the center of the flower, but it has no reproductive function. The female flower has a flat, wing-like perianth and a single ovule inside with a long, beak-like tip that protrudes from the outside of the perianth. This ovule produces a large number of seeds, which remain dormant for many years after dispersal and germinate during rare rainfall. As such, since there are traces of hermaphrodite flowers in the male flowers and the ovules are tightly enclosed by the perianth, this plant is considered extremely unique among gymnosperms, along with the closely related Ephedra and Gnetum species. The Japanese name is Sabakuomoto, and the local name is tumboa.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

ウェルウィッチア科の裸子植物。アフリカ南西部の砂漠に自生する。1860年にポルトガル領アンゴラで F.ウェルウィッチにより，また同年ナミビアのダマラランドで J.T.ベインズにより初めて発見され，J.フッカーが命名した。1属 1種の非常に珍しい植物で，その外形は他のいかなる植物とも異なる。茎の大部分は地下に埋まり，地上には倒円錐形の太い部分だけが露出する。その頂部は直径 1mぐらいの広さがあり，縁に 2枚の巨大な帯状の葉をつける。葉は年々大きくなり，数百年も生き続けて，古くなると縦に裂けたり，ねじれたりして地表に展開し，長さ 3～3.5mにも達する。雌雄異株で，いずれも円錐形の花序を茎の頂部につける。雄花には内外 2対の花被と，その内部に 6個のおしべがあり，おしべの基部は互いに癒着して筒状になる。花の中心には 1個の退化した胚珠があるが生殖機能はない。雌花は花被が平らな翼状になり，内部に 1個の胚珠があってその先端が嘴状に長く伸び，花被の外部に突き出す。この胚珠中に大量の種子を生じ，種子は散布後長年にわたって休眠して，まれに訪れる降雨のときに発芽する。このように雄花に両性花の形跡がみられ，また胚珠が花被によって硬く包まれていることなどから，近縁のマオウやグネツムの類とともに裸子植物のなかでもきわめて特異なものとされる。和名はサバクオモト，現地名はタンボア tumboaである。

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