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139. Dendrobium Swartz, Nova Acta Regiae Soc. Sci. Upsal., ser. 2. 6: 82. 1799.

石斛属 shi hu shu

Authors: Guanghua Zhu, Zhanhe Ji, Jeffrey J. Wood & Howard P. Wood

Herbs epiphytic, lithophytic, or less often terrestrial, polymorphic, deciduous or evergreen. Stems either: 1) rhizomatous, 2) erect and many noded, 3) erect and 1-noded or several noded from a many-noded rhizome, or 4) without a rhizome, new stems of many nodes arising from base of old ones; 1 or 2(-500) cm, tough or fleshy, 1 to several internodes swollen at or near base or along entire length to form canelike pseudobulbs, ± covered with sheathing leaf bases and cataphylls, often turning yellow when dried. Leaves 1 to many, alternate, apical or distichous along stem, linear, lanceolate, oblong, or ovate, sometimes subterete or terete, papery to rigid and leathery, sometimes with black or brown trichomes especially on sheath, base articulate and often with clasping sheaths, apex usually 2-lobed or emarginate. Inflorescences lateral, generally distal, in some sections pseudoterminal, 1- to many flowered, usually racemose, erect, horizontal, or pendulous; floral bracts usually insignificant. Flowers extremely variable in color and shape, often showy, very small to large, resupinate or not resupinate, usually spreading, ephemeral or long-lived. Sepals similar, free, short to filiform; lateral sepals adnate to elongated column foot and part of lip to form a mentum, 0.1-3 cm. Petals free, margin entire to fimbriate; lip entire to distinctly 3-lobed, base joined to column foot, sometimes narrowly clawed at base, sometimes forming a closed spur with lateral sepals to which it may be joined laterally for a short distance; disk with 1 to several keels, sometimes verrucose-papillose, calli rarely present, sometimes with a transverse basal ridge. Column short, stout; foot long, sometimes with a protuberance adaxially; apical stelidia obscure to distinct; viscidium present; pollinia 4 in appressed pairs, waxy, ovate or oblong, naked, i.e., without caudicles or stipes.

About 1,100 species: India across to Japan, south to Malaysia and Indonesia, east to Australia, New Guinea, and the Pacific islands; 78 species (14 endemic) in 14 sections in China.

See the monograph by Seidenfaden (Opera Bot. 83: 1-295. 1985) and the book by H. P. Wood (Dendrobiums. 2006).

After publication of the treatment for the Flora of China, one species was newly recorded from China (see JIN Xiao-Hua et al. 2010. Acta Bot. Yunnan. 32: 331-333, i.e., Dendrobium praecinctum Rchb. f.).

Key 2

1 Upper part of stem often branched; leaves linear, less than 7 mm wide, retuse; petals clavate, cordate-mucronate.   40 D. hancockii
+ Stem unbranched; leaves more than 1 cm wide, apex acute, not retuse or bilobed; petals not clavate   (2)
2 (1) Inflorescences subumbellate, almost sessile, 2-6-flowered; lip disk with 2 purplish red spots.   14 D. chrysanthum
+ Inflorescences racemose or 1-flowered   (3)
3 (2) Stems often with thickened middle and distal internodes, sometimes fusiform or slightly clavate; lip rounded   (4)
+ Stems cylindric, of even width, never swollen   (5)
4 (3) Lip with 1 transversely lunate deep purple spot, margin compoundly fimbriate.   47 D. fimbriatum
+ Lip with 2 chestnut spots, margin slightly erose.   48 D. gibsonii
5 (3) Inflorescences on leafy stems; lip golden yellow; peduncle perpendicular to stem; petals golden yellow, entire   (6)
+ Inflorescences on leafless stems   (8)
6 (5) Inflorescence 2-7-flowered; lip ± reniform-rounded, with 2 purple spots.   37 D. hookerianum
+ Inflorescence 1- or 2-flowered; lip rounded, without purple spots   (7)
7 (6) Flowers solitary in leaf axil, waxy when dry; lip ovate-rhombic, without any stripes.   41 D. lohohense
+ Inflorescences 1- or 2-flowered, very rarely solitary, racemose or subumbellate; flowers not waxy when dry.   51 D. henryi
8 (5) Floral bracts cymbiform, 15-30 mm; peduncle sheaths 5-20 mm   (9)
+ Floral bracts ovate, 2-5 mm; peduncle 3-10 mm   (11)
9 (8) Stem clavate; inflorescences stiffly arching, to 7-flowered; lip with a central maroon spot.   45 D. denneanum
+ Stem linear; inflorescences erect, 1 or 2(or 3)-flowered; lip uniformly yellow with purplish lines toward base   (10)
10 (9) Inflorescence ca. 1 cm; floral bracts membranous, white, 12-13 mm.   44 D. chryseum
+ Inflorescence ca. 6 cm; floral bracts thickly papery, pale purplish, 15-20 mm.   46 D. jiajiangense
11 (8) Flowers creamy yellow or pale yellow; lip ovate-lanceolate, margin entire.   13 D. heterocarpum
+ Flowers golden yellow; lip relatively wider, margin erose, undulate, or long fimbriate   (12)
12 (11) Lip subreniform, with purplish red stripes near base, margin erose or undulate   (13)
+ Lip suborbicular or ovate-triangular, uniformly golden yellow, margin with branched fimbriae   (14)
13 (12) Stem ± compressed fusiform, 8-15 × ca. 1.5 cm; lip margin undulate; inflorescences always 1 per node.   49 D. capillipes
+ Stem cylindric, 50-100 × 0.3-0.6 cm; lip margin erose; inflorescences often 2 per node.   50 D. dixanthum
14 (12) Petal margin densely long ciliate; lip suborbicular, margin with short branched fimbriae.   6 D. harveyanum
+ Petal margin entire; lip ovate-triangular, strongly plumose with long branched fimbriae especially along apical margin.   5 D. brymerianum

List of Keys

  • List of lower taxa


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