492 Dale . — Origin , Development , <27^ Morphological 
(Solanaceae) has been confused with them, as its name is 
a corruption of Batatas , and was at first applied to the sweet 
potato, which was introduced into Europe before the plant we 
now know as potato. 
These difficulties render the history of the Dioscoreas very 
obscure. The origin of most of the cultivated forms is either 
unknown or doubtful. According to the writer of the article 
on Dioscorea in the Dictionary of the Economic Products 
of India (’ 90 ), p. 115 et seq., the existing evidence points 
to a possible independent origin of the cultivated species 
of Dioscorea in Asia, Africa, and America. The same author 
considers that the reason why these plants were cultivated for 
food later than other vegetables is because the wild forms 
produced edible tubers without cultivation. 
All attempts to distinguish between the Linnaean species 
D» sativa and D. bulbifera , by referring to original authorities, 
in order to determine the species upon which the observations 
in this paper were made, have proved unsuccessful. The 
characters of the species in question agree with Kunth’s 
detailed description of Helmia bulbifera 1 which, according to 
Hooker 1 2 , is a synonym of D. sativa , Linn., and D. bulbifera , 
Br. Kunth himself, however, regards his Helmia bulbifera 
as identical with the D. bulbifera of Linnaeus and Wight. 
Bentham 3 regards Helmia bulbifera , Kunth, and D. bulbifera , 
Wight 4 , non-Linn., as synonyms of D. sativa, Linn. 
D. sativa , Linn., is a widely distributed plant. It grows 
wild throughout India, and is the species most generally 
cultivated, so that it is known as ‘ the common yam.’ It 
is also known in Malabar, Java, the Philippines, Australia, 
Queensland, and in the West Indies. 
References to the tubers in this species are made by the 
following authors : — 
1 Kunth, Enumeratio Plantarum, vol. v, p. 435 (’50). In the Index Kewensis 
this is said to be Dioscorea sativa. 
2 Hooker, Flora of British India, vol. vi, p. 295 (’94). 
3 Bentham, Flora Hongkongensis, p. 368 (’61). 
4 Wight, leones, vol. iii, plate 878. 
