60 



BULLETIN 934, U. S. DEPARTMENT OE 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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90-/04- 



Fig. 18. — Frequency of pots with different numbers of surviving seedlings of PiriU8 

 bankslama, 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. PytMum deharyanum 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.). 



