POTATO DISEASES IN I907. 325 



of these lots of seed, consisting of a single barrel each, were 

 planted on one side of the field under exactly the same condi- 

 tions. The plants from one of these barrels of seed were found 

 to be quite generally attacked by "black leg" late in August, 

 while not a single diseased stem could be found on the remain- 

 der of the field. A barrel of seed from this portion of the field 

 was saved for future planting. 



For a similar diseased condition Selby * has given the name 

 "potato rosette," while Rolfs has used the terms "little potato 

 disease," "collar-rot," etc.f Jones apparently prefers the name 

 "black leg" which is commonly used in England. The evidence 

 seems to be pretty conclusive that the disease as it occurred in 

 Ohio and Colorado is due to the fungus Corticium vagum var. 

 Solani, Burt., or as it is more commonly known, the potato 

 Rhizoctonia, while the similar trouble known as Schzvarsbeinig- 

 keit in Germany has been ascribed to certain bacteria. Harrison 

 has more recently described a new bacterial rot of the stem and 

 tuber due to Bacillus solanisaprus. This organism was most 

 carefully studied by him and its ability to produce the disease 

 fully demonstrated. £ The article in question was not available 

 to the writer till after the observations herein recorded were 

 made, but the evidence strongly suggests that the Maine potato 

 stem trouble is identical with Harrison's bacterial disease which 

 he states is widely distributed over various Canadian Provinces. 

 Microscopic examination of a large number of diseased stems 

 both before and after being placed in a moist chamber almost 

 invariably failed to show Rlvizoctonia hyphas. One case was 

 noted where spores resembling those of the Corticium stage were 

 observed, although they were somewhat larger than those de- 

 scribed by Rolfs. Very frequently indeed spores were found 

 which in shape and size agreed perfectly with the description 

 of macroconidia of Fusarium oxysporium, as published by Smith 

 and Swingle. § Preparations from stem where the diseased 



* Selby, A. D., Ohio Exp. Sta. Bulletins No. 139 and 145 (1903). 



t Rolfs, F. M., Colo. Exp. Sta. Buls. 70 (1902); 91 (1904). 



I Harrison, F. C, A Bacterial Rot of the Potato, caused by Bacillus 

 solanisaprus. Centralblatt f. Bakt. u. Parasitenkunde, Bd. XVII, II Abt. 

 1906. 



§ Smith, Erwin, F. and Swingle, Deane B., Bureau of Plant Industry, 

 Bulletin 55, p. 30 (1904). 



