﻿524 Dodge: Effect of host on Gymnosporangium 



methods, with sUght modifications, were employed. Branches of 

 cedar whose leaves bore son were sprayed and hung over the trial 

 host, which was then covered with a bell-jar for forty-eight hours. 

 Two or three times during this interval the bell-jar was aired out 

 and the plant sprayed. The sori of G. fraternum are so small that 

 there is little danger of killing the alternate host by over infection. 

 A larger number of plants can be more easily inoculated with a 

 small supply of teleutospore material if the sori of germinating 

 spores are shaken in a bottle with water so that the sporidia can 

 be sprayed on the plants directly. The infection chamber men- 

 tioned by Fromme (5) has been employed with great advantage. 

 This chamber is constructed by uniting five three-foot window 

 sashes in the form of a box ; the front sash is provided with hinges. 

 It is large enough to hold fifteen or twenty plants in four- or six- 

 inch pots, and plants up to two feet high can be inoculated easily 

 under such conditions. The chamber can be aired out and the 

 plants sprayed with little trouble. Another advantage to be 

 gained by the use of this apparatus is the opportunity one has 

 of providing similar conditions for several plants of different 

 species which are being tried out. The old method of using leafy 

 twigs instead of potted plants was also employed with more or 

 less success. 



The records contained in Table I* include only those cases in 

 which the recently transplanted host lived fifteen days after 

 inoculations were made. The Aronias from Newfield were badly 

 spotted with small insect galls. The percentage of positive results 

 was no doubt reduced on this account. The dates given in the 

 last four columns refer to the time at which this particular stage 

 was first observed although the fungus may have reached this 

 stage some time previously and been overlooked. Where a 

 date is replaced by a question mark (?) the aecidia were not seen 

 until dehiscence was complete. 



The plants used in these trials were chiefly species of Aronia 

 and Amelanchier. As a large number of leaves on plants of these 

 two genera first Inoculated soon showed unmistakable signs of 



* A preliminary report of this work has been published recently: Dodge, B. O. 

 Relationship between Roeslelia transformans and R. Botryapites. Torreya iS: i33. 



