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FOC | Family List | FOC Vol. 25

1. Orchidaceae

兰科 lan ke

Authors: Xinqi Chen, Zhongjian Liu, Guanghua Zhu, Kai-yung Lang, Zhanhe Ji, Yi-Bo Luo, Xiaohua Jin, Phillip J. Cribb, Jeffrey J. Wood, Stephan W. Gale, Paul Ormerod, Jaap J. Vermeulen, Howard P. Wood, Dudley Clayton & Alexandra Bell

Cypripedium flavum

Credit: Harvard University Herbaria

Perennial, but sometimes short-lived, terrestrial, epiphytic, or lithophytic, autotrophic or rarely mycotrophic herbs (or rarely scrambling vines), with rhizomes, tubers, or rootstocks with mycorrhizal fungi in roots. Stems either sympodial or monopodial, usually leafy, but leaves sometimes reduced to bractlike scales, 1 or more internodes at base often swollen to form a "pseudobulb"; epiphytic species with aerial, photosynthesizing adventitious roots, often bearing 1 or more layers of dead cells (velamen). Leaves 1 to many, alternate or occasionally opposite, often distichous, sometimes terete or canaliculate, glabrous or very rarely hairy, frequently fleshy or leathery, base almost always sheathing, sometimes articulated, sometimes forming a false petiole, margin entire, apex often emarginate. Inflorescence basal, lateral, or terminal, erect to pendulous, racemose, spicate, subumbellate, or paniculate, 1- to many flowered, flowers rarely secund or distichously arranged. Flowers small to large, often quite showy, usually zygomorphic, very rarely ± actinomorphic, bisexual [very rarely monoecious and polymorphic], sessile or pedicellate, most often resupinate with pedicel and ovary twisted through 180°, occasionally not twisted or twisted through 360°. Ovary inferior, 1-locular, placentation parietal (or rarely 3-locular and placentation axile). Sepals usually free but sometimes variously adnate, median (dorsal) one often dissimilar to laterals, laterals sometimes adnate to a column foot to form a saccate, conic, or spurlike mentum. Petals free or rarely partly adnate to sepals, similar to sepals or not, often showy; lip entire, variously lobed or 2- or 3-partite, ornamented or not with calli, ridges, hair cushions, or crests, with or without a basal spur or nectary, margins entire to laciniate. Column short to long, with or without a basal foot, occasionally winged or with lobes or arms at apex or ventrally; anther mostly 1, less often 2 or 3, terminal or ventral on column, caplike or opening by longitudinal slits; pollen usually forming distinct pollinia, less often loose, pollinia 2, 4, 6, or 8, mealy, waxy, or horny, sectile or not, sessile or attached by stalks (caudicles or stipes) to 1 or 2 sticky viscidia; stigma 3-lobed, mid-lobe often modified to form a rostellum, other lobes either sunken on ventral surface of column behind anther or with 2 lobes porrect. Fruit a capsule, rarely berrylike, usually opening laterally by 3 or 6 slits. Seeds very numerous, dustlike, lacking endosperm, rarely winged.

About 800 genera and ca. 25,000 species (some estimates as high as 30,000 species): worldwide, except for Antarctica, most numerous in the humid tropics and subtropics; 194 genera (11 endemic, one introduced) and 1,388 species (491 endemic, one introduced) in five subfamilies in China.

Recent analyses of orchids incorporating data from DNA analyses have confirmed many aspects of the established classifications but have also provided some surprises for orchid taxonomists. First of all, the results have upheld the monophyly (evolutionary integrity, i.e., the group includes all the taxa derived from an ancestral species) of the orchid family, including the apostasioids and cypripedioids. They also suggest strongly that the orchids are an ancient group that evolved in the great southern continent of Gondwanaland before it split up to form the southern continents of Australia, Africa, and South America, the island of Madagascar, and the subcontinent of India. The subfamilies Apostasioideae, Cypripedioideae, and Orchidoideae (sensu Dressler, Phylogeny Classific. Orchid Fam. 1993) are all monophyletic. However, recent work clearly shows that Vanilla and its relatives form a separate and ancient clade (an evolutionary lineage including all the taxa derived from a single ancestral one) that deserves recognition as the subfamily Vanilloideae, that the Spiranthoideae nest within a more broadly defined Orchidoideae, and that Vandoideae are a specialized clade within a more broadly defined Epidendroideae.

A detailed new classification of the orchid family is currently being produced under the title Genera Orchidacearum, of which four of the six volumes have been published and a fifth is near completion (Pridgeon et al., Gen. Orchid. 1-4(1). 1999-2005). Even when this work is completed, such is the speed with which new information and techniques are being developed and published, it will almost certainly require revision. However, we now have the broad bones of a more robust and predictive classification of the family that will be more satisfactory than the presently widely used systems that are based mainly upon morphological characters.

The classification of the family is currently the subject of some debate, particularly the circumscription and the placement of certain tribes, subtribes, and genera. The classification of Chase et al. (in Dixon et al., Orchid Conservation, 69-89. 2003), elaborated in Pridgeon et al. (loc. cit.), which is strongly supported by recent molecular, embryological, and morphological analyses, is followed here. They recognize five subfamilies: Apostasioideae, Cypripedioideae, Vanilloideae, Orchidoideae, and Epidendroideae.

Lang Kaiyong, Chen Singchi, Luo Yibo & Zhu Guanghua. 1999. Orchidaceae (1). In: Lang Kaiyong, ed., Fl. Reipubl. Popularis Sin. 17: 1-499; Chen Singchi, Tsi Zhanhuo, Lang Kaiyong & Zhu Guanghua. 1999. Orchidaceae (2). In: Chen Singchi, ed., Fl. Reipubl. Popularis Sin. 18: 1-412; Tsi Zhanhuo, Chen Singchi, Luo Yibo & Zhu Guanghua. 1999. Orchidaceae (3). In: Tsi Zhanhuo, ed., Fl. Reipubl. Popularis Sin. 19: 1-437.


Key 2: Holomycotrophic genera

1 Pollinia waxy or bony, hard or relatively hard   (2)
+ Pollinia soft or sectile   (5)
       
2 (1) Pollinia 4-6   (3)
+ Pollinia 8   (4)
       
3 (2) Plants with a slender, nearly cylindric, straight rhizome; sepals 1-2 mm; lip unlobed.   82 Risleya (p. 245)
+ Plants with a coralloid rhizome; sepals 4-10 mm; lip 3-lobed.   88 Corallorhiza (p. 252)
       
4 (2) Lip not saccate or spurred at base; leaves with neither long petiole nor pseudostem at base; column foot absent.   91 Cymbidium (p. 260)
+ Lip saccate or spurred at base; leaves long petiolate, petioles often forming a pseudostem; column foot conspicuous.   89 Eulophia (p. 253)
       
5 (1) Plants scrambling vines; fruit a pod or a long capsule; seeds with thick testa, wingless or surrounded by ± annular wing   (6)
+ Plants erect terrestrial herbs; fruit a capsule; seeds without thick testa, with narrow, long wings at both ends, ± fusiform   (8)
       
6 (5) Fruit fleshy, indehiscent; seeds wingless or with ± annular wing narrower than seed itself.   52 Cyrtosia (p. 168)
+ Fruit dry, dehiscent; seeds with broad wings, wider on one side than seed itself   (7)
       
7 (6) Stem robust; rachis, ovary, and sepals all ± covered with rust-colored hairs; column less than 1/2 as long as lip.   53 Galeola (p. 169)
+ Stem rather slender; inflorescence and flowers glabrous; column more than 1/2 as long as lip.   54 Erythrorchis (p. 171)
       
8 (5) Sepals and petals ± connate and forming a tube   (9)
+ Sepals and petals free   (11)
       
9 (8) Pollinia 2; sepals and petals united into perianth tube for almost complete length, with its apex 5-lobed, lip enclosed within perianth tube; stigma often at base of column.   67 Gastrodia (p. 201)
+ Pollinia 4; sepals and petals united into perianth tube for up to 1/2 length, lip not enclosed; stigma almost at apex of column   (10)
       
10 (9) Column wingless, with a short foot at base.   68 Didymoplexis (p. 205)
+ Column with a pair of falcate wings, without a foot at base.   69 Didymoplexiella (p. 206)
       
11 (8) Calyculus present between ovary and sepals.   55 Lecanorchis (p. 171)
+ Calyculus lacking between ovary and sepals   (12)
       
12 (11) Plants with spindle-shaped, coralloid, tuberlike, or cylindric, fleshy rhizomes, without clustered, fleshy roots; pollinarium with either caudicle or viscidium   (13)
+ Plants with shortened, relatively hard rhizomes and clustered, fleshy or fibrous roots; pollinarium with neither caudicle nor viscidium   (17)
       
13 (12) Pollinia attached ± directly to viscidium   (14)
+ Pollinia attached to viscidium by distinct caudicles   (15)
       
14 (13) Lip with a broad spur below middle; rhizome cylindric or coralloid, stout, fleshy, branched, with many scalelike sheaths.   74 Yoania (p. 210)
+ Lip without any spur; rhizome moniliform.   70 Didymoplexiopsis (p. 207)
       
15 (13) Rhizome cylindric, stemlike, decumbent; rostellum as long as anther.   15 Chamaegastrodia (p. 69)
+ Rhizomes coralloid or tuberlike; rostellum shorter than anther   (16)
       
16 (15) Lip spurless; anther with a slender filament; caudicle 1.   71 Stereosandra (p. 207)
+ Lip spurred; anther without a slender filament; caudicles 2.   72 Epipogium (p. 207)
       
17 (12) Stigma terminal; rostellum absent   (18)
+ Stigma lateral or rarely subterminal; rostellum present, usually above concave stigma   (19)
       
18 (17) Fertile stamens 2.   61 Diplandrorchis (p. 183)
+ Fertile stamen 1.   62 Holopogon (p. 183)
       
19 (17) Lip deeply 2-lobed or very rarely long acuminate at apex; rostellum often as long as anther.   63 Neottia (p. 184)
+ Lip neither deeply 2-lobed nor long acuminate at apex; rostellum conspicuously shorter than anther   (20)
       
20 (19) Lip spurred or saccate at base, with longitudinal lamellae on mid-lobe.   57 Cephalanthera (p. 174)
+ Lip neither spurred nor saccate, without longitudinal lamellae on mid-lobe.   59 Aphyllorchis (p. 177)

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