98 
Journal of Agricultural Research 
Vol. XXIX, No. 2 
paring this chart with Figure 3 in 
which depths of maximum infestation 
are distinctly different for the same 
months. 
SUMMARY 
Root-knot nematodes are often very 
numerous to a depth greater than that 
of the water table; (4) the type of the 
soil and the subsoil. The influence of 
such factors may be so great as to over¬ 
shadow any seeming seasonal change, 
or at least any that may occur between 
one month and the next. In winter 
months a considerable reduction in 
total root-knot nematode content of 
the soil appears to be evident. 
O hWJW2M2+ 4-6 eON 
Fig. 5— Depth distribution of root-knot nematodes on “hammock lahd” soil at the United States Plant 
Introduction Garden at Brooksville, Fla., from April 25; 1921, to May 5, 1922 
ordinarily reached by a plow. A con¬ 
siderable variation from one spot to 
another and from one month to an¬ 
other occurs in the depths of the 
regions of maximum infestation. Many 
factors no doubt enter into this, such 
as (1) differences in depth penetration 
of infested roots; (2) the relationship 
of time of taking soil samples to a 
period of heavy rainfall; (3) the height 
It is possible that regular seasonal 
movement does not occur to any great 
extent unless temperatures approach¬ 
ing freezing occur in the upper layers 
of soil. The experiments described 
here indicate that, in order to arrive 
at conclusive results in this regard, a 
large number of samples taken from 
different nematode-infested areas would 
have to be tested. 
