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

8. Dioscorea sect. Enantiophyllum Uline in Engler & Prantl, Nat. Pflanzenfam. 2(5): 87. 1897.

周生翅组 zhou sheng chi zu

Rootstock of vertical, usually annual tubers (renewed each year). Stem twining to right. Bulblets present or absent. Leaves opposite or alternate, simple; leaf blade broadly ovate to narrowly oblong, margin entire. Male inflorescences spikes, solitary or clustered, or grouped into axillary or terminal panicles. Flowers solitary, sessile; perianth lobes free, incurved; stamens 6, rarely 3 reduced to staminodes, anthers introrse. Female spike sometimes branched. Capsule not reflexed at maturity, usually wider than long. Seeds inserted near middle of capsule, winged all round.

About 120 species or more: mainly in tropical Africa and Asia, none common to both continents; 14 species (five endemic, one introduced) in China.

1 Stem narrowly winged, wings usually 4, sometimes more basally   51 D. alata
+ Stem terete or with 4--8 low, longitudinal ridges.   (2)
2 (1) Stem hairy when young; leaf blade sparsely hairy, apex caudate and hardened, ± sharply pointed   52 D. decipiens
+ Stem glabrous; leaf blade glabrous, apex not hardened.   (3)
3 (2) Leaf blade with sides concave due to enlargement of basal lobes, sometimes ± 3-lobed.   (4)
+ Leaf blade with convex sides, basal lobes not enlarged.   (6)
4 (3) Leaf blade often drying gray-green, often distinctly 3-lobed, less than 3 × as long as wide, ± papery; male inflorescences pendent, rachis clearly zigzagged   41 D. polystachya
+ Leaf blade drying brownish, often sagittate or hastate, sometimes more than 3 × as long as wide, often membranous; male inflorescences ± erect, rachis straight.   (5)
5 (4) Leaf blade broadly ovate to linear, not pruinose abaxially, reticulate veins not very prominent   42 D. japonica
+ Leaf blade lanceolate to linear, pruinose abaxially when fresh, reticulate veins slender but prominent   43 D. linearicordata
6 (3) Plants with fruits.   (7)
+ Plants with male flowers.   (16)
7 (6) Capsule obovoid, oblong-obovoid, or ellipsoid, longer than wide; leaf blade suborbicular or ovate.   (8)
+ Capsule oblate or conical-globose, wider than long.   (9)
8 (7) Capsule obovoid or oblong-obovoid, apex concave; leaf blade orbicular   39 D. aspersa
+ Capsule ellipsoid, apex rounded; leaf blade suborbicular to ovate   40 D. bicolor
9 (7) Leaf blade ovate-lanceolate or oblong to linear, 0.7--3(--4) cm wide, abaxially greenish white or pruinose.   (10)
+ Leaf blade not shaped as above except sometimes distally on stem, (1--)3--22 cm wide; if leaf blade shaped similarly to above then abaxially neither greenish white nor pruinose.   (12)
10 (9) Stem often prickly basally; leaf blade leathery, usually with prominent, closely spaced, reticulate veins; capsule 1.8--3.5 cm, wings 1.2--2.7 cm wide; tuber transverse section drying purplish red   45 D. cirrhosa
+ Stem not prickly; leaf blade thinly papery; capsule 1.5--2 cm, wings 1--1.5 cm wide; tuber transverse section drying pale.   (11)
11 (10) Leaf blade lanceolate to linear, 5--15 cm, base sagittate to cordate   43 D. linearicordata
+ Leaf blade oblong or obovate-oblong to ovate-lanceolate, 2--7(--9) cm, base rounded   44 D. benthamii
12 (9) Stem often 4--8-ridged; stem, petioles, and main leaf veins often drying reddish brown abaxially, leaf veins sometimes with longitudinal, whitish zone adaxially   49 D. persimilis
+ Stem terete; stem, petioles, and main leaf veins drying greenish or whitish abaxially, leaf veins without whitish zone adaxially.   (13)
13 (12) Tuber cork deciduous; leaf blade drying blackish, usually ovate or long elliptic-ovate to lanceolate, base cordate to truncate or rounded, rarely sagittate or hastate   47 D. glabra
+ Tuber cork persistent.   (14)
14 (13) Leaf blade usually elliptic-ovate to broadly lanceolate, 1.5--8(--13) cm wide   48 D. fordii
+ Leaf blade orbicular to ovate or narrowly elliptic-ovate, 4--22 cm wide.   (15)
15 (14) Leaf blade orbicular to broadly ovate, base cordate to deeply so with narrow sinus, basal lobes rounded   46 D. wallichii
+ Leaf blade ovate to narrowly elliptic-ovate, base sagittate or hastate to shallowly cordate, basal lobes bluntly angular   50 D. exalata
16 (6) Male spikes in axils of normal leaves, sometimes leaves progressively reduced to bracts distally on stem to form a terminal panicle.   (17)
+ Male spikes in specialized, lateral panicles, with bracts sharply differentiated from normal leaves.   (21)
17 (16) Male inflorescence axis distinctly zigzagged; leaf blade base rounded, apex usually with distinct, darker acumen; inflorescence spreading   44 D. benthamii
+ Male inflorescence axis straight or nearly so; leaf blade base sagittate or hastate to cordate (sometimes subtruncate or rounded and then inflorescence often ± erect), apex without distinct acumen.   (18)
18 (17) Leaf blade lanceolate to linear, more than 4 × as long as wide, abaxially pruinose   43 D. linearicordata
+ Leaf blade orbicular or oblong to ovate-lanceolate, less than 3 × as long as wide, abaxially not pruinose.   (19)
19 (18) Male flowers cuneate at base; buds ellipsoid; leaf blade drying dark brown, orbicular   39 D. aspersa
+ Male flowers truncate at base, pressed to inflorescence axis; buds ± cylindric or conical; leaf blade drying yellowish green to light brown, suborbicular to lanceolate.   (20)
20 (19) Flower buds conical; leaf blade suborbicular to broadly ovate   40 D. bicolor
+ Flower buds ± cylindric; leaf blade broadly ovate basally on stem, usually triangular-lanceolate to linear distally on stem   42 D. japonica
21 (16) Male inflorescence axis distinctly zigzagged; basal lobes of leaf blade often distinctly angular.   (22)
+ Male inflorescence axis straight.   (24)
22 (21) Leaf blade veins often drying whitish adaxially, tinged reddish abaxially   49 D. persimilis
+ Leaf blade veins not drying whitish adaxially, pale abaxially.   (23)
23 (22) Inner perianth lobes obovate   48 D. fordii
+ Inner perianth lobes spatulate   50 D. exalata
24 (21) Leaf blade greenish white abaxially when fresh, sometimes drying brown, base always rounded; tuber flesh drying purple-red, bark persistent   45 D. cirrhosa
+ Leaf blade only slightly paler abaxially than adaxially, base rounded (when tuber bark deciduous) to sagittate or hastate; tuber flesh never purple-red.   (25)
25 (24) Tuber bark deciduous; leaf base cordate to truncate or rounded, rarely sagittate or hastate; stem prickly basally   47 D. glabra
+ Tuber bark persistent; leaf base sagittate or hastate to cordate; stem not prickly   46 D. wallichii

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