96 
Journal of Agricultural Research 
Vol. XXIX, No. 2 
they were subjected. Little is known 
of the actual bionomics of this nema¬ 
tode in its free state within the soil, of 
its movements and responses to various 
stimuli, of its relations to other forms 
of soil life, etc. 
The temperatures, recorded on the 
chart for the 2- and 12-inch depths, 
show a considerable drop between Oc- 
15°. The curve drawn in the chart 
between the centers of regions of max¬ 
imum infestation should indicate any 
marked seasonal movement, if such 
occurred. While there appears to be 
a slight depression in the curve during 
the winter months, it is probably not 
sufficiently great to be significant. If 
similar nematode distribution data and 
O /-/V0/mMZ4 6-OM 
Fig. 3.—Depth distribution of root-knot nematodes in sandy loam or so-called “hammock land,” with a 
heavy clay subsoil, on United States Plant Introduction Garden at Brooksville, Fla., June 28, 1920, to 
May 28, 1921 
tober and December, but in all proba- temperature records were secured in a 
bility not enough to have much effect region farther North, where freezing 
on the vitality of the organisms. The temperatures in the upper layers of soil 
minimum temperature for the winter occur, it is possible that they would 
months at the 2-inch depth, 8° C., show a significant seasonal movement 
occurred on January 16 and again on of the nematodes in the soil. 
February 26, 1921. The lowest weekly Figure 3 gives the experimental data 
average at this depth was 17°, and the on nematode infestation’ at various 
lowest weekly average at 12 inches was depths on hammock land at the Plant 
