juneio. iQis Experiments with Coccomyces spp. from Stone Fruits 563 



Of all the experimental plants, only P. serotina (PI. 58, A) was con- 

 sistently and abundantly infected. P. mahaleh (PI. 58, B) was usually 

 infected, though ordinarily rather sparsely . In two instances, after pro- 

 longed incubation in the greehouse, P. insititia (PI. 58, C) developed 

 abundant infection. On July 30, eleven days after inoculation, two of 

 of the older leaves of P. cerasus of series 3 each bore a small group of 

 closely aggregated lesions, which appeared to be secondary infections 

 from a single primary infection on each leaf. These leaves were col- 

 lected, and no further infection had developed when the plant was last 

 noted, on October 15. Although no infection developed on the elaborate 

 control system of the outdoor experiments, the writer believes this to be a 

 case of chance infection. It is the only case found in the outdoor series. 

 The bed was the one nearest to the pathologium (about 35 feet away) in 

 which all the greenhouse inoculations were made; and it seems probable 

 that this infection resulted from wind-borne ascospores or particles of 

 atomized spore suspensions from the pathologium. This result is, there- 

 fore, not included in Table IX. 



On August 3 one leaf of P. virginiana of series 105 was observed to 

 bear numerous, closely aggregated infections. On August 7 three other 

 leaves on the same plant and one leaf of P. virginiana of series 108 were 

 found to be similarly infected. Likewise on August 3 several leaves of 

 P. cerasus of series 108 were observ^ed to bear dead brown patches on 

 which were numerous aggregated acerv^uli of a species of Cylindrospo- 

 rium. It is uncertain whether these results were due to a chance infection 

 or to delayed infection. The freedom of all control plants (PI. 58, D) 

 from infection, and the fact that in all the greenhouse series no other 

 such questionable cases occurred, are strong arguments against accepting 

 the theory of chance infection. Upon the other hand, the fact that 1 1 

 similar tests on P. cerasus and 9 on P. virginiana uniformly failed to 

 induce infection makes one hesitate to conclude that this infection 

 resulted fr®m the inoculations. These questions can be definitely set- 

 tled only by further experiments. Meanwhile these three questionable 

 cases are not included in the summary (Table IX). No other infection 

 was observed. 



REISOLATIONS 



While it was deemed neither feasible nor necessary to make reisola- 

 tions from all the crosses effected, large numbers of reisolations were 

 made from both the outdoor and the greenhouse inoculations. Especial 

 attention was given to reisolating from difficult crosses. Although the 

 slow growth of the fungi in culture made this work slow and laborious, 

 no serious difficulty was experienced in making reisolations wherever the 

 fungi fructified with fair vigor. It was important, however, to choose the 

 best possible material from which to isolate. Each reisolated strain 

 agreed closely in cultural characters with the strain from which the 

 inoculation in question had been made. 



