New York Agricultural Experiment Station. 263 



the end of June, although some spores must persist to cause infection 

 on the nearly mature fruits. 



In his former bulletin the writer did not regard the infection by 

 spores as seriously as he now does. The suggestion was made there 

 (p. 338) that carrying of diseased material on shears and saw to 

 healthy vines was probably the greatest means of spreading the 

 disease. After more extended observation and experiment it be- 

 comes obvious that the importance of shoot infection by means of 

 spores was greatly underestimated. The first intimation of the im- 

 portance of this method of infection came when a cane taken early 

 in the spring and bearing evident lesions on the peeling bark was 

 placed in a moist chamber for a few days. Great quantities of 

 pycnidia matured and exuded their spores. Further observations 

 along this line confirmed the growing suspicion that the fungus 

 might enter the more permanent wood of the spur, arm or trunk by 

 way of the infected cane tied up for bearing wood. It is not to 

 be expected that every cane which was infected the previous summer 

 will develop the disease but the number that do so is surprisingly 

 large. If only a few spots are produced on the shoot, the resulting 

 cane may bear a crop the succeeding year and be removed before 

 the fungus has had an opportunity to grow down into the more 

 permanent parts. On the other hand, if the infections are numerous 

 and the bark of the shoot broken up into a succession of roughened 

 ridges on the upper side, there is a possibility, in case the cane is 

 saved for bearing wood, that marked symptoms of the disease will 

 develop during the bearing period of the cane, and at all events the 

 probability of the fungus gaining entrance into the arm is greatly 

 increased. 



Mycelium. — The mycelium developed from the germinating spores 

 does not differ strikingly from the vegetative portions of many other 

 fungi. The individual strands are hyaline, thin-walled, varying 

 from 1.2 to 2.6 /x in diameter. The growth of the mycelium through 

 the tissue is slow. The truth of this is nowhere better brought out 

 than in inoculation experiments reported in detail elsewhere in this 

 bulletin. Figure 13 (Plate X) shows what progress was made in a 

 period of 12 months by mycelium and spores of a strain of the fungus 

 (3229) isolated July 2, 1909, from material collected at Fredonia, 

 N. Y., and inoculated into a healthy trunk on July 12, 1909. 



