546 Journal of Agricultural Research voi. xm, no. « 



heeled in in accordance with the method adopted in the preceding year's 

 work (p. 540). P. pennsylvanica and P. virginiana were collected in the 

 vicinity of Madison. In late May, after being severely pruned, the 

 plants were set in a convenient field, well removed from any known 

 source of natural inoculum of the Coccontyces spp. under investigation. 

 The plants to be inoculated were set in groups, each of which contained 

 all of the experimental species and varieties, conveniently disposed for 

 covering with a moist chamber. They formed in each plot two rows, 14 

 inches apart, with lo-inch intervals between plants in the rows. A simi- 

 larly arranged group of control plants was placed 6 feet from one end of 

 each of these plots. The number and identity of the controls varied 

 with the inocula to be used. It was planned to have in each control 

 group a cultivated cherry, a wild cherry, and a plum, including the host 

 from which the inoculum to be used was to be secured. Further con- 

 trols were added as the available supply of plants permitted. Inasmuch 

 as cross-inoculation tests with Cladosporium spp. on certain species of 

 Prunus were being conducted at the same time, the plants to be inocu- 

 lated with Cladosporium spp. were set with the controls of the Cocco- 

 myces inoculations. Thus, they served as additional controls for the 

 latter series, the inoculated plants of which, in turn, served as controls 

 for the Cladosporium series. AH beds were at least 6 feet apart. Suitable 

 cultivation was provided throughout the season, and the plants which 

 took root grew vigorously. However, owing to the bad condition in 

 which some of the nursery stock arrived, many plants failed to take root. 

 This marred considerably the completeness of the experiments. 



Apparatus. — The moist chamber illustrated in figure i was used 

 to cover the inoculated plants, while a smaller chamber of similar con- 

 struction covered the controls. This latter chamber was 33^ feet \vide, 

 6 feet long, and 4K feet high. Its roof, however, was pyramidal, rising 

 to a peak upon which the play of a single nozzle provided an adequate 

 supply of water. These chambers were connected by a 100-foot hose 

 to faucets conveniently located on a temporary pipe line. They were 

 easily handled by two men, and were very satisfactory. 



In series i, A-D, in which the plants were inoculated in their natural 

 habitat, a bell jar lined with moist paper towels was placed over each 

 plant. 



The inocula were applied by means of sterile atomizers equipped with 

 8-ounce containers and long intake tubes. In some of the experiments 

 the atomizers were operated by compressed air from a small portable 

 drum, the pressure being regulated by a cut-off. The atomizers were 

 connected with the drum by a lo-foot length of silk-covered rubber 

 tubing. This apparatus gave very good results until a defect in the 

 drum led to its disuse. A light drum with a capacity of 6 to 10 cubic 

 feet, constructed to withstand a pressure of at least 30 pounds, and con- 



