2 BULLETIN 1167, U. S. DEPARTMENT OF AGRICULTURE. 
In this country New York and a few other cities having a large 
West Indian population demand considerable quantities of the true 
yams. Previous to 1918 this demand was supplied by shipments 
from outside the continental United States; but since that time, 
when the importation was prohibited, 2 because of the danger of intro- 
ducing or further spreading in the sweet-potato regions of the country 
certain insect pests 3 common to sweet potatoes and the true yams, 
such supply as there has been has come from Florida. 
OPPORTUNITY FOR A YAM INDUSTRY IN THE SOUTH. 
With a market for yams already established and the fact demon- 
strated that the crop can be successfully grown in Florida and in the 
coast regions of other Southern States, an unusual opportunity 
seems to present itself for the development of a new crop industry 
in some of the South Atlantic and Gulf States. The present limited 
market may be expected to grow larger as more of our people come 
to realize the excellence of the yams as food. 
GENERAL DESCRIPTION OF THE TRUE YAMS. 
The vines of the true yams, unlike those of the sweet potato, are 1 
climbing and twining. The leaves are parallel veined and those of 
nearly all of the edible species are more or less heart shaped, though 
a few are divided or deeply lobed. In food characteristics the yams 
are much like the white, or Irish, potato. Most yams are white 
fleshed, while a few are yellow or purple. Some are noticeably 
sweet, but these bear less resemblance to the sweet potato than to the 
white potato. 
While yams produce underground tubers (PL I), some also bear 
aerial tubers in the leaf axils (PI. II, Fig. 2). There are edible 
kinds that bear their main crop in this way, though they are not so 
highly esteemed for food as are most of those that produce the crop 
under ground. 
KINDS OF YAMS. 
In the West Indies, whence most of the introductions of yams by 
the Department of Agriculture have been made, several species 4 are 
regularly cultivated. The principal ones are the following: Dios- 
corea alata L., the greater yam; D. cayenensis Lam., the yellow 
Guinea yam; D. esculenta (Lour.) Burkill, the lesser yam; D. lati- 
folia Benth., the acorn; D. rotundata Poir., the white Guinea yam; 
and D. trifda L. f., the yampi. 
The purpose of the present paper is primarily a consideration of 
the greater yam (Dioscorea alata L.) as a new crop industry for this 
country ; but since varieties of the other species are being tested with 
a view to their possible commercial cultivation, brief notes concern- 
ing these species are included. 
The yellow Guinea yam (Dioscorea cayenensis Lam.) as grown in 
the West Indies is an "attractive yellow-fleshed yam of good quality, 
2 Quarantines Nos. 29 and 30, U. S. Department of Agriculture, Dec. 17, 1917. Effec- 
3 The sweet-potato weevils, Cylas spp., and the sweet-potato scarabee, Euscepes 
4 For the specific identifications upon which this statement is based the writer is in- 
debted to I. Henrv Burkill, director of the Singapore Botanic Gardens, who, in collabora- 
tion with Sir David Prain (formerlv director of the Royal Botanic Gardens, Kew, 
England) has made careful studies in the genus Dioscorea. Some of the common names 
given in this paper are also used at the suggestion of Mr. Burkill. 
