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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 male flowering material

1 Male flowers sessile.   (2)
+ Male flowers pedicellate.   (10)
2 (1) Stamens 3 fertile and 3 sterile or reduced to filaments.   (3)
+ Stamens all fertile.   (4)
3 (2) Leaf blade drying green, margin usually entire, sometimes toothed; anther connectives not fork-shaped at maturity   9 D. gracillima
+ Leaf blade drying black or nearly so, margin entire though often undulate; anther connectives fork-shaped at maturity   10 D. collettii
4 (2) Leaf blade usually with short, stiff hairs or long papillae mainly along veins; anthers 3 introrse and 3 extrorse.   (5)
+ Leaf blade glabrous; anthers all similar.   (6)
5 (4) Leaf blade distinctly lobed or with strongly undulate margin, rarely margin only obscurely undulate, abaxially usually ± uniformly minutely papillose-puberulent, hairs yellowish   1 D. nipponica
+ Leaf blade ± 3-lobed, lateral lobes very short and broad, sometimes apically emarginate so leaf blade is ± 5-lobed, abaxially often papillose-hispidulous along veins, hairs white   6 D. deltoidea
6 (4) Perianth purplish red; leaf blade always drying dark, often narrowly peltate.   (7)
+ Perianth orange or light yellow; leaf blade often drying greenish, not peltate.   (8)
7 (6) Perianth lobes 1.2--1.5 × 0.8--1 mm; leaf blade triangular-ovate, usually ± 3-lobed by enlargement of basal lobes   4 D. zingiberensis
+ Perianth lobes 0.8--1.2 × 0.6--0.8 mm; leaf blade broadly triangular-ovate, sometimes 3- to obscurely 5-lobed   5 D. sinoparviflora
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 membranous, margin entire to slightly undulate; nodes usually not prickly   7 D. panthaica
+ Leaf blade slightly leathery, margin entire to completely 3-foliolate; nodes often shortly prickly   8 D. biformifolia
10 (1) Perianth purple; distal leaves usually 3-foliolate   17 D. simulans
+ Perianth orange, yellow, or green; leaves entire to deeply lobed, never compound.   (11)
11 (10) Leaf blade drying dark gray to grayish brown or nearly black adaxially.   (12)
+ Leaf blade drying green or yellow-green adaxially.   (14)
12 (11) Leaf blade of basal leaves palmately bluntly 7-lobed, uniformly hispidulous, densely so abaxially; spikes to 7 cm, usually in axillary panicles to 20 cm   11 D. futschauensis
+ Leaf blade ovate to triangular-ovate or nearly triangular-sagittate, glabrous; spikes to 20 cm, sometimes gathered into large, terminal panicles.   (13)
13 (12) Rhizomes to 5 cm thick; flowers in cymules of 2--6, rarely solitary, pedicels less than 1.5 mm; leaf blade membranous   15 D. chingii
+ Rhizomes to 1.5 cm thick; flowers solitary or paired, pedicels ca. 2.5 mm; leaf blade thinly leathery   14 D. poilanei
14 (11) Anther connectives alternately simple and forked; pedicels to 8 mm; petioles 3--12 cm.   (15)
+ Anther connectives all similar; pedicels to 3 mm; petioles 4.5--20 cm.   (16)
15 (14) Pedicels 1.5--8 mm; petioles 3--5 cm   13 D. tenuipes
+ Pedicels to 1.7 mm; petioles 5--12 cm   3 D. tokoro
16 (14) Perianth funnelform, lobes not spreading; leaf blade always entire   16 D. banzhuana
+ Perianth bowl-shaped to saucer-shaped, lobes spreading; leaf blade of basal leaves often undulate to distinctly lobed.   (17)
17 (16) Rhizome 0.7--1.5 cm thick; pedicels 2--3 mm; leaf blade orbicular to broadly ovate, usually shortly 4--7-lobed or coarsely toothed   2 D. althaeoides
+ Rhizome (1.5--)2--5 cm thick; pedicels to 1.5 mm; leaf blade triangular or ovate-cordate to unequally 3--7-lobed, often very variable in shape.   (18)
18 (17) Flowers usually in cymules or umbellules of 2--4(--7), solitary distally on inflorescence; stamens inserted at middle of perianth lobes; leaf blade drying yellowish green abaxially   1 D. nipponica
+ Flowers solitary or paired; stamens inserted at base of perianth; leaf blade drying grayish white abaxially   12 D. spongiosa

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