ISTew Yokk Agricultural Experiment Station. 261' 



into the drop of water, setting up unequal tension and producing 

 darting, whirling motions. 



As the spores are exuded from the pycnidia, spattering drops of 

 rain carry them to young shoots a few feet away while many are 

 washed to the shoots immediately under the infected arm. As is 

 usually the case, however, the majority of the spores are washed to 

 the ground where they perish. The spores find conditions favorable 

 for germination in the clinging drops- of water which persist on the 

 shoots for many hours during periods of continued fog and rain. 

 Ordinarily the temperature is quite low at such times. In 1912, for 

 example, the chief and almost the only infection of the season 

 occurred throughout the Chautauqua and Central Lakes regions on 

 May 28th and 29th. These were days of continuous mist and fog. 

 Foliage of trees and vines was completely enveloped in moisture 

 but the fog was not heavy enough to cause dripping from the foliage 

 except in case of slight puffs of air. It seems quite certain that 

 infection in 1909 occurred on May 28th also. Careful records were 

 being kept in a vineyard at Romulus for the black-rot infection 

 periods. The first black-rot infection of the year occurred on that 

 date and it is believed that most if not all of the infection by Cryp- 

 tosporella occurred at the same time. 



Spore germination. — No attempts have been made to germinate 

 spores of the fungus at the same time that infections were probably 

 taking place under natural conditions. Under more favorable 

 conditions as to temperature it has been possible to germinate the 

 spores, so that they had long germ tubes at the end of 18 to 24 hours. 

 Many attempts have been made to germinate spores on detached 

 leaves and stems in order to study the entrance of the germ tube. 

 Unfortunately no cases have ever been observed. 



Meteorological relations. — From what has been said above in re- 

 gard to the exudation of pycnospores it may be inferred that weather 

 conditions play an important role in the dissemination and occur- 

 rence of this fungus. It will be recalled that moisture is required 

 for the exudation of spores. Clinging drops of water are necessary 

 for the germination of spores and these drops must persist for a 

 number of hours. Since the major infections of the season are 

 known to occur during the early growth of the vine, that is, during 

 the development of the first three or four internodes, the conditions- 

 favorable for infection may be said to be a relatively low tempera- 



