|
Thelymitra is a genus of orchids known as 'sun orchids' in reference to their habit of only opening in warm weather. == Description == They are about 100 species distributed in higher rainfall areas across Australia (with 50 or so species), New Zealand (10+ endemic species), New Caledonia (2), Timor, Java, and the Philippines. The type species is ''Thelymitra longifolia'' J.& G. Forst. 1775 from the South Island of New Zealand. The scientific name Thelymitra was given by J. R. and G. Forster, botanists on Captain Cook's second voyage. The genus name is derived from the Greek words ''thely'' (woman) and ''mitra'' (mitre hat), referring to elaborate shape of the staminodal (staminode = sterile stamen) structure at the top of the column, called a mitra. These terrestrial orchids are only above ground during spring and early summer, usually with a single leaf, growing up from two underground tubers. It is elongated or linear-lanceolate and glabrous. The Custard Orchid (''T. villosa'') is the only species with a hairy leaf. The leaves of ''T. spiralis'' and ''T. variegata'' are spirally twisted. The flower stalk is usually a bluish-green colour. The flower stem usually carries 4 to 10 flowers (even up to 20 flowers in the Plain Sun Orchid, ''T. holmesii''), often opening all at once, though some species have only one flower each year. The flower size is between 1 and 6 cm. These flowers only open in bright sunlight (in combination with warmth and humidity), close at night and during cold or cloudy weather. Sun orchids exhibit a particular characteristic : their lip shows, except in a few species such as ''T. variegata'', almost the same shape, colour, colour pattern or size as the other petals and sepals. This gives a symmetrical shape to the perianth. Furthermore the lip lacks ornamentation. In other orchid genera, the lip has a distinctive shape and colour. The particular shape and color of the sun orchids mimics the flowers of lily family (Liliaceae) and the family Goodeniaceae, aiming by deceit for the same insect pollinators. The Slender Sun Orchid (''T.pauciflora'') only opens for a short time (or not at all) and is self-pollinating. This self-pollination is a successful strategy followed by several other species such as and ''T. circumsepta'', ''T. graminea'', ''T. holmesii'' and ''T. mucida''. Once the weather dries out the leaf shrivels away and the orchid lies as a single spherical tuber. Sun orchids come in most colours, including purple, deep blue (''T. pauciflora''), white, pink, magenta, maroon, yellow (''T. antennifera'') and red (''T. x macmillanii''). Most are a single colour or have spots, a few have stronger variation and are multi-coloured. The deep blue colour, found in about 75% of the sun orchids, is of a rare kind, found only in 5 other orchid genera. Several species are considered by the IUCN as endangered (''T. epipactoides'') or critically endangered (''T. gregaria'', ''T. hiemalis'' and ''T. x mackibbinii''. A number of conservation measures are underway in South Australia. Until shortly, the taxonomy of the genus was outmoded and understudied. Jeffrey A Jeanes of the Royal Botanic Gardens Melbourne has recently (2004) done a taxonomic revision, resolved several species complexes and described a considerable number of new species (see ''Muelleria'' 19; 2004) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Thelymitra」の詳細全文を読む スポンサード リンク
|