10 BULLETIN 1167, U. S. DEPARTMENT OF AGRICULTURE. 
Another pest to which yams are subject is the common root-knot 
nematode or eelworm {Heterodera radicicola). The injurious effects 
of root-knot are somewhat less marked than with the dasheen and 
some other crops, but severely infested yam tubers become warty 
and rough in appearance (PI. V, Fig. 1) and consequently less de- 
sirable either for home use or for market. Seed yams affected with 
root-knot should be treated while dormant with hot water (122° F.) 
for 40 minutes, in order not only to give the young plants a better 
chance if the soil is already infested, but also to avoid the possibility 
of introducing this injurious plant parasite into ground previously 
free from it. 
VARIETIES OF THE GREATER YAM. 
As stated elsewhere, there are many varieties of the greater yam 
throughout the tropical world; but only those that at this time ap- 
pear to have especial interest for southern growers will be considered 
here. Since the names of the varieties most Avidely tested in the South 
are uncertain, these varieties with a single exception will be desig- 
nated by their seed and plant introduction (S. P. I.) numbers only. 
Limited quantities of these, whenever available, will be furnished 
by the Bureau of Plant Industry to persons in suitable localities 
who desire to experiment with them. Other varieties and other 
species are under test, and when definite information concerning 
them is available it is hoped to make it the subject of another publi- 
cation. 
S. P. I. NO. 37943. 
The history of this unnamed variety, as far as it is known, has 
been given on page 4. The tuber is white fleshed and without pro- 
nounced coloration in the inner skin. The vine is prominently 
4-angled and winged, and the leaf is rather long, heart-shaped, and 
dark green in color. The tubers are usually of medium to large 
size — up to 15 pounds in weight — and are of very good quality, 
though not equal to some of the varieties tested which have been 
recently introduced direct from the West Indies. For some time 
after it is harvested No. 37943 generally contains a little more 
moisture than is desirable. ( 
As stated in the quotation from Mr. DeHoff's letter concerning 
this variety it does fairly well in rather light sandy soils, but in- 
creased yields are obtained in rich soils. In drained muck soil in 
the Florida Everglades in 1921 small smooth tubers were produced 
by this variety. The small size may have been due to the smallness 
of the tubers planted, however. While this variety is not a favorite 
on the market, it sells readily in the absence of better ones. 
S. P. I. NO. 47001. 
Yam No. 47001 (PL IV, Fig. 2), obtained by the Department of 
Agriculture more than 15 years ago from a grower at Lemon City, j 
Fla., is similar to No. 37943 in vine, leaf, and tuber characters, ex- 
cept that the flesh of the former variety is still more moist and has 
less flavor. Chemical analysis indicates the starch content to be less 
than 14 per cent. The variety appears to be one of several which 
are classed under the general name Agua (water) yam in Porto 
Rico. The vine is more tender and brittle than that of the pre- 
ceding variety, and seldom bears aerial tubers. The variety does 
