On the Origin, Development, and Morpho- 
logical Nature of the aerial Tubers in 
Dioscorea sativa, Linn. 
BY 
ELIZABETH DALE, 
rfeiffer Student , Girton College , Cambridge . 
With Plate XXVJ. 
T HE species Dioscorea sativa was founded by Linnaeus 
in 1 7 53 but, according to Bentham 1 2 , nearly all 
modern authors have transposed the names of this and another 
Linnaean species, D. bulbifera ; perhaps because both pro- 
duce aerial tubers in the leaf-axils. Hooker 3 states that 
‘ the species of Dioscorea are in a state of indescribable 
confusion.’ Another source of difficulty in determining the 
species of Dioscorea is the use of the English name ‘ Yam/ 
because earlier writers applied it indiscriminately to any 
edible underground tuber, so that, at first, it included Batatas 
( Ipomoea ) edidis (the sweet potato, one of the Convolvulaceae), 
Manihot utilissima (cassava, one of the Euphorbiaceae) and 
the aroid Amorphophallus campatiulatus . Even the potato 
1 Linnaeus, Species Plantarum, vol. ii, p. 1033 (1753). 
2 Bentham, Flora Australiensis, vol. vi, p. 462 (’73). Flora Hongkongensis, 
p. 368 (’61). 
3 Hooker, Flora of British India, vol. vi, p. 288 (’94). 
[Anrals of Botany, Vol. XV. No. LIX. September, 1901.] 
