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FOC | Family List | FOC Vol. 24 | Dioscoreaceae | Dioscorea

1. Dioscorea sect. Stenophora Uline in Engler & Prantl, Nat. Pflanzenfam. 2(5): 84. 1897.

根状茎组 gen zhuang jing zu

Rootstock a horizontally spreading, perennial rhizome. Stem twining to left. Bulblets present or absent. Leaves alternate, usually simple, rarely 3-foliolate; leaf blade glabrous or shortly stiffly hairy, margin entire to deeply palmately lobed. Male inflorescence a spike, raceme, or thyrse, sometimes branched, sometimes gathered into a terminal panicle by reduction of subtending leaves. Flowers usually in cymules of 2--4, solitary distally on inflorescence, sessile or pedicellate; bracts borne at base of pedicels; perianth lobes connate at base; stamens 6, sometimes 3 reduced to staminodes. Capsule reflexed at maturity, about as long as wide, rarely longer than wide. Seeds inserted near middle of capsule and winged all round, rarely inserted near base with wing pointing toward capsule apex.

About 35 species: temperate Asia, extending into Malaysia and W to the Caucasus and Balkans, a few species in North America; 18 species (eight endemic) in China.

Several species are of medicinal importance.

Key based on fruiting material

1 Seeds inserted near base of capsule with wing pointing toward capsule apex, wing ca. 3 × as long as seed.   (2)
+ Seeds inserted near middle of capsule, winged all round.   (4)
2 (1) Leaf blade margin usually entire, rarely obscurely undulate   3 D. tokoro
+ Leaf blade margin deeply lobed to obscurely undulate.   (3)
3 (2) Leaf blade abaxially glabrous or sparsely minutely hairy   1 D. nipponica
+ Leaf blade abaxially densely shortly pilose along veins   2 D. althaeoides
4 (1) Capsule pruinose, drying blue-black; leaf blade drying blackish, often narrowly peltate.   (5)
+ Capsule not pruinose, drying pale to dark brown; leaf blade never peltate.   (6)
5 (4) Leaf blade triangular-ovate, usually ± 3-lobed by enlargement of basal lobes; capsule about as long as wide   4 D. zingiberensis
+ Leaf blade broadly triangular-ovate, sometimes 3- to obscurely 5-lobed; capsule longer than wide   5 D. sinoparviflora
6 (4) At least some leaves 3-foliolate.   (7)
+ Leaves entire to deeply lobed, never compound.   (8)
7 (6) Leaves usually 3-foliolate, lateral leaflets subequaling middle leaflet   17 D. simulans
+ Leaves often entire, lateral leaflets ca. 1/2 as long as middle leaflet, often incompletely separated   8 D. biformifolia
8 (6) Leaves often prickly on petiole and sometimes along main veins; stem with many prickles proximally   18 D. birmanica
+ Leaves not prickly; stem not prickly or inconspicuously prickly at nodes (more easily felt than seen).   (9)
9 (8) Leaf blade slightly leathery, main veins often conspicuously pale; stem often shortly prickly at nodes.   (10)
+ Leaf blade membranous to papery, main veins not pale; stem not prickly.   (11)
10 (9) Capsule 2.8--3.2 cm; leaves always simple   14 D. poilanei
+ Capsule ca. 1.5 cm; distal leaves often 3-lobed to ± 3-foliolate with small, lateral leaflets   8 D. biformifolia
11 (9) Leaf blade usually distinctly lobed or toothed at margin, occasionally coarsely undulate, often abaxially papillose to hispidulous.   (12)
+ Leaf blade entire to distinctly undulate at margin, occasionally obscurely 3-lobed.   (15)
12 (11) Leaf blade adaxially hairy   11 D. futschauensis
+ Leaf blade adaxially glabrous.   (13)
13 (12) Capsule wings 1.5--1.6 cm wide; rhizome 2--5 cm thick, drying soft and spongy; basal leaf blades sometimes subequally 5--9-lobed or coarsely toothed   12 D. spongiosa
+ Capsule wings 0.8--1.4 cm wide; rhizome often less than 2 cm thick, drying ± solid; basal leaf blades ovate to unequally 3(or 5)-lobed.   (14)
14 (13) Leaf blade papery, often abaxially hispid along veins; capsule wings (0.7--)1.2--1.4 cm wide   6 D. deltoidea
+ Leaf blade membranous, glabrous; capsule wings 0.8--1.2 cm wide   16 D. banzhuana
15 (11) Leaf blade drying green, margin sometimes toothed.   (16)
+ Leaf blade drying dark brown or black, margin entire to slightly undulate.   (17)
16 (15) Leaf blade 5--10(--12) × 2.5--7 cm   9 D. gracillima
+ Leaf blade 10--18 × 6.5--11 cm   13 D. tenuipes
17 (15) Capsule yellowish brown, 2.4--2.7 cm; leaf blade drying dark brown   7 D. panthaica
+ Capsule brown to dark brown, 1.5--2.1 cm; leaf blade drying ± black.   (18)
18 (17) Capsule wings 0.8--1.1 cm wide   10 D. collettii
+ Capsule wings 1--1.7 cm wide   15 D. chingii

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