Amitostigma
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Amitostigma Schltr. 1919, is a genus in the orchid family (Orchidaceae).
It is an exclusively Asian genus of 27 orchids, growing in the alpine habitats of east Asia, India, eastern Himalaya, China, and Japan to Kuril Islands. Twenty two species of this genus grow in China.
These are dwarf terrestrial orchids, including some myco-heterotrophic species. The globose or ovoid tubers (1 to 1.5 centimetres) of these autotrophic plants are fleshy and not lobed, with several slender roots. New shoots grow each tuber.
The stem is usually erect, with one (or rarely two or three) basal or cauline (stem) leaves. The length of the stem can vary between 5 and 45 centimetres.
The green leaf blade is not articulate and can have an oblong, lanceolate, elliptic, or ovate form, even within the same species (see A. lepidum). The leaves appear at the time of expansion of the flower (anthesis).
The terminal inflorescence is racemose, seldom subcapitate. The floral bracts are often lanceolate. The cylindrical to fusiform ovary is resupinate (turned upside down).
Each inflorescence shows many (rarely one or two) flowers. These are also resupinate and usually twisted to one side.
The sepals are completely separate from each other, with an oblong to ovate appearance, and usually singly-veined. The erect petals are straight, often slightly broader than the sepals. The three- or four-lobed lip is usually longer and broader than the petals and sepals, spurred at the base. The mid-lobe is oblong, square, or ovate. The margin of the lip is often slightly undulate.
They have a characteristic short column. The erect anthers are cohesive with the column through its broad base or back. They have two parallel locules with farinaceous, sectile pollinia. The small rostellum is beak-shaped, attached with its folded end to the viscidium. The two protruding stigmas are slightly club-shaped.
The capsule is suberect.
The color may vary within the same species: Amitostigma lepidum may show a purple lip with white margins, or a white lip with purple dots or a totally white lip. Even the leaves may vary from lanceolate to ovate within the same species.
After flowering, the leaves turn yellow color and die off. The plants then starts its summer dormancy for several months. This cycle is well adapted to a climate which is hot and dry in summer.
Species
- Amitostigma alpestre : Alpine Chicken Orchid (Taiwan).
- Amitostigma amplexifolium (SC. China)..
- Amitostigma basifoliatum (China).
- Amitostigma bifoliatum (China).
- Amitostigma capitatum (China) .
- Amitostigma dolichocentrum (China) .
- Amitostigma faberi (China)
- Amitostigma farreri (Tibet)..
- Amitostigma gonggashanicum (China).
- Amitostigma gracile (China to Temp. E. Asia).
- Amitostigma keiskei (Japan)
- Amitostigma keiskeoides (Vietnam).
- Amitostigma kinoshitae (S. Kuril Is., Japan - Hokkaido, N. Honshu).
- Amitostigma kurokamianum (Japan - Kyushu: Mt. Kurokami).
- Amitostigma lepidum : Okinawa Orchid (Japan - S. Kyushu to Nansei-shoto.
- Amitostigma monanthum (SE. Tibet to C. China).
- *Amitostigma monanthum var. forrestii (Tibet). Tuber geophyte
- *Amitostigma monanthum var. monanthum (SE. Tibet to C. China). Tuber geophyte
- Amitostigma papilionaceum (China - NW. Sichuan).
- Amitostigma parciflorum (China).
- Amitost
igma physoceras (China - Sichuan)..
- Amitostigma pinguicula (China).
- Amitostigma simplex (hina - W. Sichuan, SW. Yunnan)..
- Amitostigma tetralobum (China - SW. Sichuan, N. Yunnan).
- Amitostigma thailandicum (Thailand).
- Amitostigma tibeticum (Tibet).
- Amitostigma tominagai (Taiwan).
- Amitostigma trifurcatum (China)..
- Amitostigma yueanum (China - Yunnan).
