422 Report of the Mycologist of the 



A quantity of badly diseased tubers was obtained and planted 

 on land whicli had not grown potatoes for at least ten years. 

 The tubers were cut with two eyes to each piece and care was 

 taken that every piece planted showed some of the disease. 

 Nearly every piece of " seed " produced a i)lant, but many of 

 them were very slow about coming up. They appeared weak, 

 were of divers sizes and, up to the time of blossoming, were con- 

 siderably smaller than plants from healthy " seed " planted at 

 the same time. 



It was late in July before any of the plants showed symptoms 

 of the disease, and at the close of the season only a few had had 

 even a mild attack. When the tubers were dug just a few 

 showed the characteristic blackening of the fibro-vascular bun- 

 dles at the stem-end. 



In spite of their slow growth in the early part of the season 

 they yielded well. Five rows fifty feet long yielded 275 pounds 

 of merchantable tubers which is equivalent to a, yield of 266 

 bushels per acre. It is evident that they were not badly dis- 

 eased. 



Were the disease due either to fungi or bacteria, diseased 

 tubers would, most likely, produce diseased plants. Since the 

 disease is located in the subterranean stem, and to some extent 

 in the tubers themselves, it is in the highest degree probable that 

 the germs of the disease would become attached to the tubers 

 and be distributed with them. The results of this experiment 

 furnish strong evidence that the disease is not communicable, 

 which is equivalent to saying that it is not caused by any vege- 

 table organism. That the weather conditions were not unfavor- 

 able to the disease is shown by the fact that a potato field about 

 thirty rods from the experimental potatoes was badly affected 

 and the disease was common in various localities on Long Island. 

 It should be stated, however, that the plants were thoroughly 

 sprayed with Bordeaux mixture (eight or nine times in the course 

 of the season); but it is scarcely possible that spraying could 

 prevent a disease like this in which the seat of the trouble is 

 certainly below the surface of the soil. Moreover, we observed, 



