Naturalisation in Extra-Tropical Countries. 169 



Dioscorea Japonica, Thunberg. 



The hardy Japan-yam. Not prickly. The material here for 

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

 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 and large size; 

 the tubers are eaten by the savages raw when young, roasted when 

 aged [E. Palmer]. 



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. a man's arm ; their taste exceedingly 

 good. Roxburgh's plant of this name seems quite different. 



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 piperifolia, Humboldt and Bonpland. (D. subhastata, Vellozo.) 

 From Panama to Peru and Brazil. The tubers keep particularly 

 well, and are often smoked for preservation. Starch about 26 per 

 cent. [Dr. Th. Peckolt]. Tubers roundish, attaining a weight of 

 6 Ibs.; mucilaginous. 



Dioscorea purpurea, Roxburgh. 



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



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. esurientum (Fenzl) from Guatemala, D. tube- 

 rosa 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 their adapta- 

 bility to field-cultivation require to be more fully ascertained. 



Dioscorea spicata, Roth. 



India. Roots used like those of other species, so those of D. 

 Hamiltoni, J. Hooker. 



Dioscorea spinosa, Roxburgh. (D. sativa, Linn<$, partly.) 

 South-Asia extensively ; also cultivated elsewhere. 



