540 Journal of Agricultural Research voi. xiii, no. n 



TECHNIC OF INOCULATIONS 



Experimental plants.'' — In each experiment, the following plants 

 were used: Prunus cerasus L. (Montmorency Stark), P. avium 1,. A 

 (Windsor), P. avium B (seedling), P. mahaleh L., P. pennsylvanica ly. 

 f., P. serotina Ehrh., P. padus L., P. virginiana L., P. domestica L. 

 (Lombard), P. insititia L. (Shropshire), P. americana Marsh. A (De- 

 Soto), P. americaiia B, P. salicina Lindl. (Burbank), P. munsoniana 

 Wight and Hedrick (Wild Goose), Amygdalus persica L. (Elberta), A. 

 persica nectarina Ait. (Boston), P. armeniaca L. (Alexander), and P. 

 hesseyi Bailey. 



Except in cases where varietal names are given, the experimental 

 plants were seedlings or cuttings. They were i-to-2 -year-old trees ob- 

 tained, so far as feasible, from reliable nurseries in the upper Mississippi 

 Valley. P. americana and P. virginiana were collected in the vicinity 

 of Madison. The identification of all species was confirmed. The trees 

 were assembled in the spring and heeled in until the middle of May, when 

 they were severely pruned and set in the pathological garden in such 

 fashion that suitable groups might be covered by moist chambers. Each 

 group consisted of two rows, 14 inches apart, in which the plants were 

 set at lo-inch intervals, except near the middle, where a 3-foot space 

 was left in order to facilitate the manipulation of the moist compart- 

 ments. Each plot contained one tree of each experimental species or 

 variety, and in all plots the plants were grouped in the same order. The 

 plots were disposed at intervals of 12 feet in the direction of the rows, 

 and 6 feet laterally. Adjacent to each plot and not nearer than 5 feet 

 to plants to be inoculated was set a group of three controls, one of which 

 was of the species from which the inoculum to be used vv^as to be isolated. 

 Suitable cultivation was provided throughout the season, and the plants 

 grew vigorously. 



Apparatus. — In order to insure favorable humidities and tempera- 

 tures for infection, it was necessary to devise special apparatus. Accord- 

 ingly, two movable moist chambers, 6 to 8 feet long, 33^ feet wide, and 

 2,14 to 4 feet high, were constructed so that they could be set over the 

 experimental plants. One was made of glass and wood (see fig. 2), and 

 the other of light galvanized iron over a wooden frame. The latter was 

 provided with glass doors which admitted enough light to keep the plants 

 under fairly normal conditions while covered. These chambers were 



1 In this paperthe experimental plants are listed in all cases in the order most advantageous for comparing 

 results from the inoculation tests. When two or more varieties or strains of the same species were used, 

 they were designated, respectively, by appropriate letters (A, B, etc.). In nomenclature Wight's usage 

 was followed where applicable. (Wight, W. F. native American species of prunus. U. S. Dept. 

 Agr. Bui. 179, 75 p., 4 fig., 13 pi. 1915) The writer wishes to express his indebtedness to Mr. Wight for 

 personal advice in these matters and for verifying the identification of certain species. In varietal names 

 of plums and cherries, the usage of Hedrick was followed. (Hedrick, U. P. the plums of new york. 

 616 p., col. pi. Albany, N. Y., 1911. and Hedrick, U. P. the cherries of new york. 371 p., col. pi. 

 Albany, N. Y., 1915.) 



