32 
Reviewing our own work and observations, these assumptions 
apparently have considerable truth in them, but they do not appear 
to express the whole truth. Among the enormous number of inocu- 
lations made during the past four seasons, several common factors 
have been observed running through them all. In our greenhouse 
experiments during the winter months very little or no difference in 
the percentage of infection or the rate of progress of the disease has 
been observed between plants sprayed with tap water immediately 
preceding inoculation and other plants of the same age and vigor 
inoculated when dry. The same infection relations also have held 
between greenhouse inoculations made in sunlight and those made 
on cloudy days or under shade. 
On the other hand, striking differences are often shown among 
plants in varying states of vigor or age. After inoculation, badly 
stunted or old plants have in general shown a very much lower per- 
centage of infection and slower progress of the disease than young 
vigorously growing plants of the same variety. These facts have 
repeatedly been observed during the progress of our studies, and for 
this reason great care has been exercised in selecting plants for viru- 
lence tests. 
From these observations, together with the beetle and wilt curves 
and the meteorological data obtained in field experiments (figs. 2 to 
4), it appears that within rather wide limits weather conditions have 
very little direct effect on the percentage of infection. However, a 
rapid, sappy growth of the vines favors infection and spread of the 
disease through the plant; whereas senility in the host, whether due to 
normal maturity or to unfavorable conditions such as drought or lack 
of plant food, furnishes conditions unfavorable to infection and spread 
of the bacteria within the plant. Thus, by inducing rapid succulent 
growth of the vines rainy weather may indirectly raise the percentage 
of infection and increase the reproduction of the bacteria inside of the 
plant. If, then, following such a rainy period the sun suddenly comes 
out hot, any tendency to wilt will obviously become evident at once. 
Indeed, under these circumstances, the excessive transpiration from 
too rapidly growing tissues often causes transitory wilting where no 
parasitic organisms are present. On the other hand, after a long 
period of drought the prevalence of wilt often decreases, not directly 
because of the weather conditions but because the vines have hard- 
ened up and no longer favor infection. Furthermore, periods of 
drought often come at midseason when senility is normally approach- 
ing, and the weather conditions serve only to hasten and intensify 
the natural process of ripening. A decrease in number of cucumber 
beetles between broods often comes simultaneously with these mid- 
season drought conditions and this again reduces the number of infec- 
tions at their source. Undoubtedly an extremely dry atmosphere 
