juneio. i9i8 Experiments with Coccomyces spp. from Stone Fruits 545 



In series 5 the fungus from P. virginiana induced abundant infection 

 on its original host, moderate infection on P. mahaleh, and light, delayed 

 infection on P. insitiiia. 



In series 6, inoculated with a 14-month-old strain from P. cerasus, 

 infection was rather sparse and somewhat slow in developing, despite 

 the fact that the inoculum contained abundant, vigorously viable spores. 

 Abundant infection developed on P. avium and sparse infection on P. 

 cerasus and P. mahaleh. Rather abundant infection developed after a 

 more prolonged incubation period on P. munsoniana and P. hesseyi. 



The fungus from P. avium (series 7) infected P. avium abundantly and 

 P. cerasus and P. mahaleb rather sparsely. After a prolonged incuba- 

 tion period, P. hesseyi also developed abundant infection. 



Numerous reisolations were made in the same manner as in 191 7 

 (P- 563), and with like results. 



EXPERIMENTS OF 1917 



In 191 7 the outdoor tests were supplemented by extensive greenhouse 

 experiments. By starting potted plants early in the spring, it was found 

 possible to have them in leaf as soon as the ascospores of the fungi 

 under investigation approached maturity (their maturity can be has- 

 tened in the laboratory). Thus, it was possible to conduct extensive 

 experiments, without danger of natural infection, before the outdoor 

 plants were ready. In this way essentially the equivalent of two years' 

 data was secured in one season. I^'urthermore, it was possible to study 

 infection under varied experimental conditions more readily in the green- 

 house than out of doors. The danger of falling into errors of interpreta- 

 tion of the results obtained under greenhouse conditions seems ade- 

 quately guarded against by the extensive outdoor tests of two seasons. 



TBCHNIC OF INOCULATIONS 

 OUTDOOR EXPERIMENTS 



ExPERiMElNTAiv PLANTS. — The following plants were used: Prunus 

 cerasus (Montmorency Stark), P. avium (Yellow Spanish), P. mahaleb, 

 P. pennsylvanica, P. serotina A, P. serotina B, P. serotina C, P. padus, 

 P. virginiana, P. domestica (lyOmbard), P. insititia (Damson Shropshire), 

 P. americana A (De Soto), P. americana B, P. salicina (Burbank), P. 

 munsoniana (Wild Goose), Amygdalus persica (Elberta), P. armeniaca 

 (Superba), and P. hesseyi. 



Two consignments of P. serotina which were received under erroneous 

 labels were included in the experiments for purposes of comparison. 

 Plants of P. serotina were accordingly distinguished as to source by the 

 letters "A," "B," and "C." 



Except in cases where varietal names are given, the experimental 

 plants were seedUngs or cuttings. They were obtained, assembled, and 



