2 D. Prain & I. H. Burkill — On Bioscorea deltoldea, etc. [Siipplt. 



Dioscorea deltoidea, D. sihkimensis, D. Prazeri^ and D. panthaica "which 

 are found in the lower Himalaya and mountains east of it : they are 

 all closely allied. Next stands rather alone D. acerifolia from Central 

 China. Thirdly come the three closely allied Japanese species D. sejp- 

 temloha, D. nipponica and D. qninqueloha. Lastly staiid two species 

 from Japan, D. tenidpes and D. Yokusai, associated with D. enneaneura 

 from Central China. Uline, who has recently done valuable work 

 upon the genus Dioscorea, refers some of the species to a section which 

 he names Stenophora ; but it is not clear to us if he would so refer all. 

 We therefore leave undiscussed for the present the question of sections. 



Dioscorea hirmanica, which we described in a recent paper, is allied 

 to the yams under discussion ; but, with the horizontal inedible rhizome 

 and dependent female inflorescences and the censer mechanism for seed 

 distribution, it combines leaves not constricted or lobed, as well as a 

 robustness which is foreign to all except, it may be, D. acerifolia ; 

 moreover none are thorny to the degree that it is, and none have pre- 

 cisely similar cymules of male flowers. 



The following is a key to the species which we shall forthwith 

 describe : — 



Anthers not didymous : — 



Leaves qnite smooth beneath : — 



Male flowers not pedicelled ... ... ... ... Prazeri. 



Male flowers pedicelled ... ... ... ... sihkimensis. 



Leaves with hairs or papillae beneath : — 

 Male flowers sessile : — 



Male iafloresoence slender, little branched ,., ... deltoidea. 



Male inflorescence much branched, subthyrsoid ... ... 'panthaica. 



Male flowers stalked : — 



Male inflorescence long and rigid ... ... ... acerifolia, 



Male inflorescence slender : — 



Leaves 7-lobed, lobes acute ... ... ... septemloha. 



Leaves 3-5-lobed, lobes obtuse : — 



Capsule longer than Avide ... ... ... nipponica. 



Capsule as wide as long ... ... ... qninqueloha. 



Anthers didymous : — 



Perianth segments equal ... ... ... ... tenuipes. 



Perianth segments unequal : — 



Male flowers in cymules, larger ... ... ... Yokusai. 



Male flowers solitary or in pairs, smaller ... ... enneaneura. 



Dioscorea. Prazeri. Bhizoma ci-assam, aliquanto informe, parum 

 hypogeeum, venenosum, carne albo. Oaulis e radice singulus, glaber, 

 sinistrorsum volubilis, teretiusculus, iiiertnis, viridis, bulbifer. Folia ^A- 

 terna, chavtacea, utrinque glaberrinia, subtus glauca, pel hicide punctata, 



