New York Agricultural Experiment Station. 113 



brown in colar. When the hyphge occur in scab ulcers, those 

 near the surface are brown, while the deeper-lying ones are color- 

 less.' The sclerotia on the stems and those on the tubers are 

 essentially the same. They are irregular in outline and vary in 

 size from a mere speck to the size of half a pea or even larger. 

 When dry they are dirt colored, and it is difficult to distinguish 

 them from particles of soil adhering to the tubers. This prob- 

 ably accounts for their having been so generally overlooked. But 

 when wet they become dark brown and very conspicuous, par- 

 ticularly on the light skinned varieties of potatoes. In spite of 

 vigorous washing, sufficient to thoroughly remove the soil from 

 the tubers, the sclerotia remain firmly attached. Two house- 

 keepers whose attention we have called to the* matter assure us 

 that they have long observed that when potatoes are prepared 

 for baking there are often found dark brown irregular bodies 

 which are exceedingly difficult to remove by washing. It is neces- 

 sary to use a scrubbing brush to get rid of them. We suspect 

 that these sclerotia are well known to many of the more observant 

 housekeepers. 



The amount of damage done by the Rhizoctonia when it attacks 

 the subterranean stem and roots of the potato is as yet undeter- 

 mined, but that the fungus is, in some cases at least, a parasite 

 there is little doubt. Where it occurs on the tubers, all of our 

 numerous observations go to show that it is not injurious to 

 them. While the Rhizoctonia hyphse may be abundant in scab 

 ulcers there is no evidence that they have anything to do with 

 the formation of the ulcers. The sclerotia are usually seated 

 on the uninjured &kin of the tuber. A tuber may bear hun- 

 dreds of sclerotia and yet be absolutely sound. In this respect 

 our Rhizoctonia appears to differ from the European potato 

 Rhizoctonia. Some writers report that the latter is a common 

 cause of potato rot. In other respects the two forms are strik- 

 ingly similar. We are under obligations to Prof. Dr. Paul 

 Sorauer of Berlin for excellent fresh specimens of the European 

 Rhizoctonia solani, from which cultures for inoculation work have 

 been obtained, 



8 N 



