259 



AN EXPERIMENT. 



For the past three years we have had occasion daily to pass the home 

 of Mayor Elmore, of Crawfordsville. On the lawn in front of bis house 

 stands a large cedar and just southeast of it, about three rods distant, 

 is a small apple tree, about seven years old. During the spring of IIXJO 

 we noticed the great abundance of the cedar apples which infested this 

 cedar and later in the summer the great number of leaves of this apple 

 tree that were covered with the Iloestelia. That the cedar galls were re- 

 sponsible for the attacks on the apple tree seemed quite evident, but we 

 decided to test it by an experiment the following spring, and also to de- 

 termine if by exclusion of the spores of the cedar galls the apple tree 

 might not be protected from the ravages of the lioestelia. Accordingly 

 on April 24. lIJiil, one of the limbs of the apple tree was enclosed in a 

 sack of cheesecloth. The apple leaves were just bursting from the buds 

 and the teleutospores had as yet not ripened on the cedars. Almut May 1. 

 just after a hard rain, the first gelatinous stalks with their teleutospores 

 made their appearance on the cedar apples, and on the following day 

 sporidia in alnmdance were produced. On May 27 the first indication 

 of the Roestelia, in the form of yellow spots or patches, appeared on the 

 exposed leaves of the tree. Examination of the protected leaves showed 

 only a very few spots. By July 3 no aecidia had ripened, although sper- 

 magonia in abundaaice had been produced. .July 27 the first aecidia ma- 

 tured. The sack had been removed .Tune 25 and the protected leaves 

 showed only about one-half as many spots as the unprotected. No more 

 spots appeared on any of the leaves during the remainder of the season. 

 The last crop of sporidia were produced about the last of May. at least a 

 month before the sack had been removed. 



It was also observed that the west side of the apple tree, which was 

 directly exposed to the cedar, bore more clusters of aecidia per leaf than 

 the east side. This fact, together with the results in the protected brajich, 

 seems to prove conclusively that the sporidia of the teleutospores on the 

 cedar had produced the infection of the apple leaves. The failure of the 

 sack to exclude all of the sporidia was due to their minute size and the 

 openness of the cloth. The experiment will be repeated next spring with 

 cloth of a firmer texture. The fact that infection took place through the 

 cheesecloth proves that the sporidia and not the teleutospores are car- 



