356 
Journal of Agricultural Research 
Vol. XXXI, No. 4 
in the Manor loam and Leonardtown silt loam. The results with 
potting soil were very erratic, possibly because of the presence of 
excess humus or of chemical fertilizers. The data on the influence 
of the size of soil particles indicate that there would have to be a 
very decided difference in the proportions of very coarse or o very 
fine particles to markedly influence penetration. Hence if pene¬ 
tration in preliminary tests varies greatly from that expected it 
seems more likely that the chemical composition of the soil is re¬ 
sponsible than that it is due to a variation in physical make-up too 
slight to be noticeable to the eye. 
Soil moisture is constantly changing in the regions where wart is 
prevalent, because of alternating spells of rain and of dry weather. 
As the percentage of moisture present has a marked influence on 
penetration, it would be necessary to determine the soil moisture at 
frequent intervals in order to give the most economical treatment 
ana to insure proper penetration. Where possible, it would be ad¬ 
vantageous to treat the soil while wet or just previous to rainy 
weather, as less water and materials would be required for adequate 
penetration. As shown in Tables VII and IX and in the discussion 
on the effect of applying all of the chemicals in part of the water and 
following with the remainder of the water as such, the penetration is 
improved by following this procedure. This indicates that a heavy 
rainfall within a reasonable time after the application of the strong 
chemical solution might eliminate the necessity of applying the 
water. Autumn applications, particularly, might eliminate the ex¬ 
pense of much of the water. The application of chemical solutions 
requires special apparatus and the exercise of considerable care to 
secure even distribution. Relatively simple apparatus can be used 
in applying water. Laborers would demand more pay for handling 
any of the dangerous chemicals than for handling water. One man 
with a hose could probably apply a much larger quantity of water 
than one or more men operating an expensive chemical outfit even 
if there were no delays to refill the chemical outfit. 
Much stronger tests are obtained in the soil near the line of maxi¬ 
mum penetration when part of the water is applied after the chem¬ 
icals have been applied. Tests made throughout the soil penetrated 
indicate a much more even distribution of the chemicals by this 
method. Hence it might be possible to use a more dilute initial 
solution at a great saving in chemicals. 
The tests of penetration in tubes having a high-water table were 
made because some infected soil is bottom land with a water table 
near the surface. It was thought that adequate penetration in such 
land would be impossible as long as the water table remained high. 
The results obtained in the laboratory indicate that where this water 
table was stationary or receding, satisfactory penetration could be 
secured. The solution might not be effective much below the actual 
water line, however, as it would soon become greatly diluted even if 
the depth of penetration were adequate. 
Some of the wart-infected soils contain rocks, stones, or debris. 
If a solution applied to these soils would not penetrate to spores 
underneath sucJi obstacles, extermination by chemical treatments 
would become correspondingly complicated. The few experiments 
on lateral and upward penetration were performed to get informa¬ 
tion on the amount of penetration under obstacles. The results were 
