IN EXTRA-TROPICAL COUNTRIES. 107 



Dioscorea hastifolia, Nees. 



Extra-tropical Western Australia, at least as far south as 32 

 It is evidently one of the hardiest of the Yams, and on that 

 account deserves particularly to be drawn into culture. The tubers 

 are largely consumed by the local aborigines for food ; it is the only 

 plant on which they bestow any kind of cultivation, crude as it is ; 

 fit for arid situations, but seemingly fond of lime. 



Dioscorea Japonica, Thunberg. 



The hardy Japan Yam. Not prickly. The material here for com- 

 parison is not complete, but seems to indicate that D. transversa, 

 R. Br. and D. punctata, R. Br., are both referable to D. Japonica. 

 If this assumption should prove correct, then we have this Yam 

 along the coast-tracts of North and East Australia, as far south as 

 latitude 33. In Australia we find the wild root of good taste. 



Dioscorea nummularia, Lamarck. 



The Tivoli Yam. Continental and insular India, also South Sea 

 Islands. A high, climbing, prickly species, with opposite leaves. 

 Roots cylindrical, as thick as an arm ; their taste exceedingly good. 



Dioscorea oppositifolia, Linne. 



India and China. Not prickly. One of the edible yams. 



Dioscorea pentaphylla, Linne. 



Continental and insular India, also South Sea Islands. Likewise a 

 good yam. A prickly species, with alternate divided leaves. 



Dioscorea purpurea, Roxburgh. 



India. In Bengal considered next best to D. alata. 



Dioscorea quinqueloba, Thunberg. 



Japan, and there one of several yam plants with edible tubers. 

 Among numerous congeners are mentioned as providing likewise 

 root vegetables : D. piperifolia (Humboldt) from Quito, D. esurien- 

 tum (Fenzl) from Guatemala, D. tuberosa and D. conferta (Vellozo) 

 from South Brazil, D. Cayennensis (Lamarck) from tropical South 

 America, D. triphylla (Linne) from tropical Asia, D. deltoidea 

 (Wallich) from Nepal. Of these and many other species the relative 

 quality of the roots, and the degree of facility of their field cultiva- 

 tion, require to be more ascertained. 



Dioscorea sativa, Linne. 



South Asia, east as far as Japan, also in the South Sea Islands, 

 and North and tropical East Australia, likewise recorded from 

 tropical Africa. Stem cylindrical, not jpjsflfcdy^- ^JThe acrid root 



