60 
BULLETIN 934, U. S. DEPARTMENT OF AGRICULTURE. 
A test made on jack pine with a culture of Phytophthora cactorum, 
furnished by the department of plant pathology of Cornell Univer- 
sity, resulted negatively. At the time of sowing the seed three pots 
were inoculated with cultures on nutrient agar inserted at several 
points in each pot. After emergence additional fragments of prune- 
agar cultures were placed in contact with the seedlings, and they were 
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Fig. 18. — Frequency of pots with different numbers of surviving seedlings of Pinus 
banksiana, inoculation experiment No. 31. The solid lines represent pots to which 
cultures of saprophytic organisms were added. The broken lines are based on pots to 
which no saprophytes had been added. The solid lines are based on 78 pots in the 
upper graph and 80 pots in the lower one ; the broken lines on 33 pots in the upper 
and 25 pots in the lower graph. Pythium debaryanum was added just after sowing the 
seed at a single point in each pot represented by the two upper lines. Cultures of 
saprophytes were applied broadcast two days before the Pythium inoculations were made. 
sprayed with a spore suspension. The pots were covered with glass 
to increase atmospheric moisture, and the seedlings were occasionally 
sprayed with an atomizer. The soil was an autoclaved mixture in 
which simultaneous inoculations in a different room with Pythium 
and Corticium proved successful. The failure of the Phytophthora 
may possibly have been due to the lower temperature at which the 
pots inoculated with it were kept (15° to 20° C.). 
