YAM CULTURE IN PORTO RICO. 11 
and small rooted kinds. The ridges for planting were made in 
the usual way and in soil that was well adapted to the crop. The 
plants made thrifty growth and were pruned back each week, the 
Guinea to 6 feet and the Potato variety in one plat to 2 feet, in an- 
other to 4 feet, and in a third to 6 feet. Plats of each variety were 
left unpruned for checks. The vines of the Potato variety continued 
thrifty through the season, but the pruned vines of the Guinea 
variety lost some of their rich color before fall and became dry 
several weeks earlier than the check plat. The harvest from the 
pruned plants of the variety Guinea was only 46 per cent of the yield 
obtained from the check plat. The yield from the Potato variety 
was 29 per cent from the vines pruned to 2 feet, and 46 per cent 
from those pruned to 4 feet, while the yield from plants pruned to 
6 feet was 68 per cent of that obtained from the check plat. 
This clearly shows that the vines should not be pruned or injured 
if the best results are expected. Where the vine supports were in- 
sufficient or allowed to blow over and were not promptly replaced, 
there was a marked decrease from the normal yield. Vines not pro- 
vided with supports, but allowed to creep over the ground, made 
very poor growth and gave low yields of roots. 
HARVESTING. 
Such implements as mattocks, heavy forks, and spades are required 
for harvesting yams, because the earth must be removed to the depth 
of the roots. The large roots fit firmly in the soil and it requires great 
care to remove them without injuring them. They will be bruised if 
pulled or pried out before the soil around them is well loosened or 
removed. The process of digging deep-rooted types in heavy soils is 
difficult in dry weather, because the roots are often enlarged near the 
lower end and are easily injured during removal from the hard soil. 
Roots of all varieties of yams are subject to rapid decay if they are 
bruised or the skin is broken. When bruised to any depth they soon 
become unfit for use. The yam, like the potato, is used while it is 
fresh, and every precaution should be taken to keep it from decay- 
ing, so that the entire crop can be utilized. 
VARIETIES AND CULTURAL TREATMENTS RECOMMENDED. 
Among the following are some well-known varieties that have been 
grown for years for home and market consumption in every part of 
Porto Rico. Some others mentioned are not as yet well known, hav- 
ing only recently been introduced into the island, and probably into 
the West Indies. A number of the latter varieties have desirable 
properties, and are considered among the best in flavor and quality, 
deserving trial in all parts of the island. The varieties discussed in 
