YAM CULTURE IX PORTO RICO. 17 
The vines of this variety are long, large, vigorous, and angular and 
have four sides. A membrane, or wing, running the length of the 
vine is found at each corner. The leaf petiole is from 5 to T inches 
long and has five wings which are formed at its angles, the same as 
those on the vine. These extend into the five largest veins on the 
lower surface of the leaf. Enlarged purple sections J to f inch 
long' grow near each end of the petiole. The blade of the leaf is 
6 by 4 or 5 inches, and if is dark green. A few small air tubers 2 by 
1J inches develop on the vines of this variety. The edible root is 
almost spherical or made up of two or three large round lobes. How- 
ever, it never forms long, deep-growing roots. Usually a slight 
depression occurs at the union with the rootstock. The surface of 
the root is rough, corky, and dark gray. The interior is a rich 
purple and has some areas where the coloring is not so intense. The 
starch content in the fresh root is 20.03 per cent. After being cooked, 
this yam has a smooth, even texture and retains its dark purple color, 
causing it to resemble the well-known variety locally known as 
Mapuey morado. Its flavor is rich and pleasing and has been highly 
complimented by all who tested it. Unfortunately, the distribution 
of the Purple Ceylon, as well as the area planted to it, has been some- 
what restricted. Its edible qualities cause the entire crop to be con- 
sumed year after year, and the result is that only the rootstock is 
left for planting. 
DIOSCOREA SATIVA. 
The yam grown at the station as S. P. I. Xo. 31922 has been iden- 
tified, from specimens sent from here, by W. E. Safford. of the 
Bureau of Plant Industry, United States Department of Agriculture, 
as a varietv of D. sativa. This varietv, original! v from New Guinea, 
is of all the varieties tested the only one that produces vine tubers, 
or " air potatoes," of sufficient size to be suitable for table use. Its 
yield of these is sufficiently high to justify its being planted more 
extensively. The vines of this yam are large and make rampant 
growth. Under normal field conditions they sometimes attain a 
length of 25 feet. The leaves appear opposite on the vine and have 
large, almost round petioles that are 5 or 6 inches long. The blades 
are from \.\ to 6 inches in width and from 6 to 7 inches long. Near 
each end of the petiole there is a purplish section which is from f to 
1 inch long and considerably larger than the remainder. The edible 
roots are irregular in shape and usually develop from the rather long 
rootstock four to eight finger-like lobes, some of which are divided 
or branched. The whole roots weigh only 1 or 2 pounds. (PI. V. 
fig. 1.) The skin is very thin and tough, and would be smooth were 
it not for numerous small rootlets. The inner part of the skin and 
