94 
Journal of Agricultural Research 
Vol. XXIX, No. 2 
For the first series of experiments 
the samples were placed in cloth bags 
covered with a double wrapping of 
heavy waxed paper. These were 
packed in canvas bags, the four samples 
from each depth together, and the 
entire lot packed in crates and shipped 
to Washington. The soil was then 
placed in 6-inch pots under good grow¬ 
ing conditions in the greenhouse, and 
set to tomato seedlings, three to a pot. 
In about six weeks, when the earliest 
infections had reached maturity, and 
before the production of any secondary 
infections, the plants were removed, 
the roots washed, and readings taken 
on number of root knots per pot. 
In the second series of experiments 
the soil samples were collected direct 
Smith, who, because of his long con¬ 
tact with the nematode experimental 
work, had a very good conception of 
relative degrees of infestation. It 
was found by a few counts that such 
estimates were sufficiently accurate 
for the purpose. 
Unfortunately, some features of 
these experiments that should ordi¬ 
narily have received more attention had 
to be neglected, owing to the pressure 
of work elsewhere. 
RESULTS 
In the first series of experiments, 
made with an extremely sandy loam soil 
at Brooksville, Fla., collections and 
plantings were made at intervals of a 
Fig. 1—A diagram representing the trench dug for collecting soil samples at different depths 
from the field into 6-inch pots, and 
the tomato plants grown in them in 
the propagation houses at the Plant 
Introduction Garden at Brooksville, 
Fla. 
As stated above, the measure of the 
relative nematode content of the 
various soil samples was the number of 
knots that developed on the roots of 
the tomato plants grown in them. At 
first actual counts were made. Based 
on these counts, a scale was adopted 
to indicate the relative numbers as 
follows: 1 to 100 knots, few; 100 to 
200, medium; 200 to 400, numerous; 
400 to 600, very numerous; above 600, 
extreme. The experiments conducted 
the second year were based not on 
actual counts but on estimates, 
recorded in the terms just cited. 
These estimates were made by Robert 
little more than a month, a total of 10 
being conducted from June 28, 1920, 
to May 27, 1921. The soil samples 
throughout were shipped to Washing¬ 
ton, D. C., and plantings of tomatoes 
made in the greenhouse. At approxi¬ 
mately six weeks after planting, in each 
case, the plants were lifted, the roots 
carefully washed, and notes taken on 
the relative abundance of root-knot 
infestations. 
The chart (fig. 2) shows graphically, 
the relative depth distribution of the 
root-knot nematodes at different dates. 
In examining this chart it should be 
borne in mind that differences in infes¬ 
tation may not be significant as sea¬ 
sonal variations. More probably any 
great difference between one month and 
the one preceding or following it, for 
example, is due to distinct differences 
