548 



Journal of Agricultural Research voi. xni, no. n 



plants were usually readily differentiated, such inoculations being made 

 on the recently developed foliage of the rapidly growing twigs. 



GREENHOUSE EXPERIMENTS 



ExPBRiMBNTAiy PLANTS. — The experimental plants were from the same 

 sources and of the same species and varieties as those used in the 

 outdoor tests (p. 545). They did not, however, include all the species 

 used in the field. The plants were assembled in early April, severely 



Fig. 2. — Moist chamber used in the greenhouse inoculation experiments: A, galvauized-iron pan, with 

 drainage outlet B; C, strips of board to support chamber; £>, sphagnum or sand. Dimensions: Length, 

 6 feet; breadth, 32 inches; height of front, 4J4 feet. This chamber was also used in the outdoor inocula- 

 tions of 1916 (p. 540). 



pruned, and set in 6- to lo-inch flowerpots. The pots were submerged 

 in the soil in a greenhouse of the garden type, and the plants were given 

 suitable cultural attention. To inhibit the development of insect pests, 

 particularly the red spider, the plants were washed daily with a strong 

 spray from an angle nozzle conveniently connected with the water supply. 

 Throughout the early spring the temperature of this greenhouse ordinarily 

 ranged between 21° and 27° C. In late spring and early summer the 

 maximum temperature was frequently considerably higher. 



Apparatus. — Suitable conditions of humidity were obtained by 

 placing the inoculated plants in the moist chamber illustrated in figure 2. 



