YAM CULTURE IX FORTO RICO. 19 
portion the lobes are very tender and almost pure white. The skin 
on the upper portion is rough and corky ; on the lower portion it is 
thin and easily broken. The roots are susceptible to injury at harvest 
time, because they develop well below the surface of the ground, have 
brittle interiors, and are large and oddly shaped. So that harvesting 
may be facilitated with least possible injury to the roots, banks should 
be made as high as those required for the longer-rooted kinds. In- 
jured roots decay much more rapidly than those of most varieties, 
but uninjured specimens retain their tenderness and good texture as 
long as any other large-rooted kinds. Upper sections of the root- 
stock, when planted simultaneously with equal-sized pieces from the 
lower part of the root, made an average yield per plant which was 
practically the same for the different plats. It would therefore seem 
that under favorable conditions any part of this yam can be used for 
planting. 
AGUA. 
The Spanish name Agua, meaning water, is given to a number of 
varieties of Dioscorea cdata. and is used to indicate one particu- 
lar type of yam that is probably more widely known than any 
other in Porto Rico, but which is usually ranked as a second- 
class yam. Its popularity is in great measure due no doubt to its 
abundant yield on a wide range of soils and to its peculiar keeping 
qualities after being removed from the ground a long time. The 
vines of the Agua are moderate growers and four-sided, having 
rather wide membranous wings running along their corners. The 
margins of these wings, like the margins of the leaves, are purplish. 
The leaf blade is normally 4 or 5 inches long, and 3 J or 4 inches wide, 
and the petiole is about 5 inches long. The large cylindrical or 
tapering roots are very dark, rough, and thick-skinned. While the 
outer layer of the skin is tender, the inner yellow layer is exceedingly 
hard. The interior of the root has at the base a marked brownish 
tinge, which decreases toward the lower end. When boiled, the root 
has a slightly yellowish watery color. The edible portion contains 
considerable fiber, but otherwise the texture is of good quality. 
This variety sells at a lower price than most yams, because it lacks 
the rich flavor found in other varieties. Like all other large-rooted 
varieties, it should be planted on high ridges. In Porto Rico the 
notion seems general that to produce roots of marketable size, either 
the crown or top of the old root should be planted. Experience has 
shown, however, that almost identical results can be obtained from 
top or bottom sections when planted in well-prepared banks. 
The starch content of this variety was found to be 16.76 per cent 
of the fresh yam. This is considerably below the average for all 
