Dioscorea. ] DIOSCOREACEX. . 251 
laminate, embryo between the laminz with a suborbicular cotyle- 
don.—Species about 150, in tropical and subtropical regions.— 
‘The tubers of Dioscorea, known as yams, contain much starch, 
and are largely cultivated in India and in other tropical countries. 
‘The following key to the species of Dioscorea which occur either wild 
or cultivated within the area of this flora is based on Prain and 
Burkill’s Synopsis of the Dioscoreas of the Old World (Africa exclud- 
ed) and was published in Journ. and Proc. As. Soc. Beng. (N. 8.) 
Vol. X No. 1, 1914. 
Stems twining to the left :— 
Section Compriium. Tubers produced in a 
bunch, spreading, edible. Leaves simple, 
cordate. Male flowers 1-2 together on a 
long spike-like raceme (when the 2nd 
flower is present it is placed cymosely on 
the pedicel of the lst); perianth saucer- 
shaped, the stamens inserted near the 
margin, Seeds unknown :— 1. D. aculeata. 
Section Lasropuyton. Tubers _ vertical. 
Leaves generally compound. Male flowers 
in spikes or spike-like racemes which are 
generally compound ; perianth-lobes just 
united at the base, with the stamens in- 
serted on them ; filaments simple. Seeds 
winged on one side only, in elongated, 
reflexed or horizontal capsules :— 
Male flowers not densely packed ; stamens 
3; leaflets 3 or 5 é ° ° - 2 Dz. pentaphylla. 
Male flowers densely packed; stamens 
6; leaflets3  . ° ° . &. Dz triphylla, 
Section OpsopHyton. Tubers vertical. 
Leaves simple, cordate. Male flowers in 
characteristic dependent spikes ; perianth- 
lobes with the stamens inserted at their 
bases; filaments free. Seeds with the 
wing developed on one side only, in 
elongated reflexed capsules :— 
Leaves alternate, ovate-cordate, drying 
green ; flower-spikes long; tubers some- 
times slightly elongating u : . 4. D, bulbifera. 
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