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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 to species

1 Leaf sheaths insignificant; inflorescence pendulous, arising from leaf axil near stem apex; flowers yellow or white tinged with yellow, never with green   (2)
+ Leaf sheaths distinct; inflorescence and flowers without above combination of characters   (7)
2 (1) Stems 1-leaved, 4-angled   (3)
+ Stems 2-5-leaved, terete or laterally compressed, sometimes with many angles or ridges   (4)
3 (2) Inflorescence much longer than stem, many flowered; stems to 10 cm; adaxial surface of lip with only base and center pubescent, margin glabrous.   7 D. lindleyi
+ Inflorescence shorter or slightly longer than stem, 1-3-flowered; stems 3(-5) cm; entire adaxial surface of lip pubescent.   8 D. jenkinsii
4 (2) Sepals and petals white; stem with many ridges; leaves usually 1.5-2 cm apart; inflorescence dense; lip entire, orange.   12 D. thyrsiflorum
+ Sepals and petals yellow   (5)
5 (4) Inflorescence dense; dorsal sepal ca. 1.5 cm; petal margin finely dentate; upper side of lip rather long ciliate, more sparsely so toward edges; leaves borne close together on a many-angled stem; floral bracts to ca. 2.4 cm.   11 D. densiflorum
+ Inflorescence lax; dorsal sepal 1.8-2 cm   (6)
6 (5) Stems distinctly laterally compressed, clavate; petal margin entire; lip margin minutely erose to ciliate-hairy.   9 D. sulcatum
+ Stems not laterally compressed, thickly fusiform, with many ridges; petal margin minutely dentate; lip margin undulate.   10 D. chrysotoxum
7 (1) Leaves and leaf sheaths with dark hairs, at least when young   (8)
+ Leaves and leaf sheaths glabrous   (15)
8 (7) Mentum saccate, 4-13 mm   (9)
+ Mentum narrowly conic (shaped like a candle snuffer), 15-30 mm, forming spur   (12)
9 (8) Sepals and petals white   (10)
+ Sepals and petals yellow; stems 5-21 cm   (11)
10 (9) Lip with mid-lobe reflexed, yellow to orange, lateral lobes bright red, disk with 5 irregularly papillate ridges; stems obovoid to nearly globose.   58 D. bellatulum
+ Lip not reflexed, white with darker throat, disk with 3 granulose lamellae.   59 D. christyanum
11 (9) Stems 5-11 cm, 12-15 mm in diam.; dorsal sepal strongly keeled abaxially; ovary prominently 3-ribbed; mentum ca. 4 mm.   60 D. trigonopus
+ Stems to 21 cm, 3-4 mm in diam.; dorsal sepal not keeled; ovary rounded; mentum 10-13 mm.   61 D. sinense
12 (8) Ovary 3-ribbed; spur ± curved, often sigmoid.   64 D. cariniferum
+ Ovary terete or somewhat rounded-clavate; spur straight   (13)
13 (12) Petals broadly ovate, ca. 40 × 32 mm, much wider than sepals.   63 D. wattii
+ Petals oblong, lanceolate, or oblong-elliptic, 15-20 × 4-10 mm, narrower than sepals or nearly equally wide   (14)
14 (13) Flower opening widely; petals and sepals nearly equal in width; sepals dorsally keeled.   65 D. williamsonii
+ Flower narrowly tubular; stem pendulous; petals narrower than sepals; sepals thickened along dorsal midvein, but not alate.   62 D. longicornu
15 (7) Stem with a few internodes near base swollen into a spindle-shaped pseudobulb, remainder of stem narrowly cylindric or laterally compressed   (16)
+ Stem without any group of swollen internodes, uniformly narrowly cylindric or laterally compressed   (19)
16 (15) Leaves leathery, dorsiventrally compressed.   71 D. crumenatum
+ Leaves fleshy, laterally compressed or cylindric   (17)
17 (16) Leaves laterally compressed and shortly ensiform, base 3-4 mm wide.   72 D. equitans
+ Leaves terete, cylindric, or subterete   (18)
18 (17) Leaves terete, 1.5-2.5 mm wide at base; lip mid-lobe papillose.   73 D. exile
+ Leaves slender, hairlike, less than 1 mm wide.   74 D. pseudotenellum
19 (15) Leaves thick and fleshy, cylindric, subcylindric, or laterally compressed and ensiform   (20)
+ Leaves flat with distinct abaxial and adaxial surfaces   (23)
20 (19) Leaves subcylindric, almost subulate or laterally compressed and shortly ensiform, 1-4 mm wide; flowers white or pale yellow, lip spotted yellow; mentum 1-2 cm   (21)
+ Leaves laterally compressed and broadly ensiform, 5-6 mm wide; flowers very small, white, lip tinged with red, or pale yellowish white; mentum 5-7 mm   (22)
21 (20) Leaves ensiform; flowers large; mentum to 2 cm; lip with 2(-4) thickened raised veins, densely papillose distally.   77 D. parciflorum
+ Leaves almost subulate; flowers smaller; mentum less than 1 cm; lip smooth.   78 D. hainanense
22 (20) Stems to 60 cm, leaves smaller toward stem apex; flowers in groups of 2 or 3 along terminal part of stem.   75 D. spatella
+ Stems to 23 cm, leaves uniform along stem; flowers subterminal.   76 D. terminale
23 (19) Leaves elliptic, subcordate and clasping at base, distichous, connivent to one another; flowers borne on leafy stems; sepals and petals reflexed.   52 D. ellipsophyllum
+ Leaves not as above   (24)
24 (23) Stem evenly narrowly cylindric (internodes never swollen), surface glossy, rigid; leaves narrow, grasslike; inflorescence 1- or 2-flowered   (25)
+ Stems cylindric or compressed, sometimes upper part thickened and clavate, internodes swollen or not, with longitudinal stripes or ribs, sometimes entirely enclosed in leaf sheaths, fleshy; leaves grasslike or not   (29)
25 (24) Flowers white; inflorescences axillary along lower part of leafless stem, without protective sheaths.   39 D. leptocladum
+ Flowers yellow or yellowish green; inflorescence axillary along leafy stem, emerging from a protective sheath and piercing subtending sheath, appearing opposite next proximal leaf   (26)
26 (25) Lip entire, spatulate or narrowly lanceolate; sepals and petals obtuse to rounded.   1 D. salaccense
+ Lip distinctly or indistinctly 3-lobed; sepals and petals long acuminate   (27)
27 (26) Flowers not opening widely; lip rhombic, mid-lobe ovate-triangular, margin fimbriate, disk pubescent.   2 D. furcatopedicellatum
+ Flowers opening fully; lip not as above, disk glabrous   (28)
28 (27) Lip mid-lobe ovate, long acuminate, margin undulate.   3 D. somae
+ Lip mid-lobe oblong, obtuse, margin not noticeably undulate.   4 D. luzonense
29 (24) Plants short, grasslike; inflorescences borne laterally from leaf axils, usually from distal nodes on current year’s mature stem, nearly erect and parallel to stem, with many small flowers; sepals less than 2 mm wide   (30)
+ Plants tall, not grasslike; inflorescence exserted, but never erect and parallel to stem, with a few to many medium-sized to large flowers; sepals more than 3 mm wide   (34)
30 (29) Lip entire, elliptic.   66 D. porphyrochilum
+ Lip 3-lobed   (31)
31 (30) Inflorescence ca. as long as leaves; lip pale green, suborbicular.   69 D. compactum
+ Inflorescence longer than leaves   (32)
32 (31) Lateral lobes of lip entire or slightly inconspicuously toothed.   70 D. sinominutiflorum
+ Lateral lobes of lip with comblike teeth   (33)
33 (32) Base of sepals and petals with purplish red venation, entire lip deep purplish violet.   67 D. strongylanthum
+ Sepals and petals white or yellow, lateral lobes of lip purplish violet.   68 D. monticola
34 (29) Mentum long, spurlike or tubular   (35)
+ Mentum short and broadly blunt   (36)
35 (34) Flowers white with pale purple veins; stems often branched.   56 D. chameleon
+ Flowers pale to dark purple; stems unbranched.   57 D. goldschmidtianum
36 (34) Lip saclike or slipperlike, margin strongly involute   (37)
+ Lip not saclike or slipperlike, margin spreading to recurved   (38)
37 (36) Stems cylindric; leaf 10-15 cm; inflorescence to 10-flowered; dorsal sepal 24-35 mm.   42 D. moschatum
+ Stems strongly compressed; leaf 6-8 cm; inflorescence 1-flowered; dorsal sepal ca. 16 mm.   43 D. menglaense
38 (36) Lip boat-shaped or subglobose, mid-lobe deflexed, acuminate   (39)
+ Lip not as above   (40)
39 (38) Stems swelling toward apex from a narrow basal portion; column foot ca. 2.5 mm, much shorter than column proper; lip hypochile much larger than epichile, deeply concave, subglobose, with orbicular sides embracing column, entire inner surface finely ciliate, epichile triangular-acute, inner surface glabrous, ecallose.   53 D. hercoglossum
+ Stems ± of equal width, not swollen distally; column foot ca. 10 mm, much longer than column proper; lip hypochile reduced to a neck, epichile cymbiform, finely pubescent at apex and along median line, glabrous toward margin, with a large glossy basal central callus.   54 D. aduncum
40 (38) Flowers white, lip with a yellow patch; sepals ca. 8 mm; lip conspicuously 3-lobed, margin finely toothed above middle, front margin densely long ciliate-hairy; inflorescence 2-flowered.   55 D. stuposum
+ Flowers often not white; sepals more than 10 mm; lip entire or inconspicuously 3-lobed, adaxial surface usually papillose to pubescent, sometimes with a callus near base but without any other ornaments; inflorescences 1-4-flowered   (41)
41 (41) Sepals and petals pale yellow, creamy yellow, or golden yellow, never tinged with purple or any other color except on lip.   Key 2
+ Sepals and petals purplish red, white, or pale yellowish green, turning pale or creamy yellow, apex often purplish red.   Key 3

List of Keys

  • List of lower taxa


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