The Sterile Fungus Rhizoctonia. 



T3 



we observed that some of the so-called "deep scab" ulcers were 

 filled with inyceliuin composed of rather coarse hyph^e. Micro- 

 scopic examination showed the hyphai to be those of Bhlzoctonia. 

 These tubers had been bought at a grocery in Geneva. Other 

 tubers were then obtained from other groceries 

 and also direct from potato fields in the vicinity 

 of Geneva, and it was found iXmi It hi zoctonia 

 liyphie are of frequent occurrence in seal) ulcers. 

 The next advance made was the discovery of 

 the RMzoctonia sclerotia on the tubers and 

 stems. On September 21 Mr. Rolfs found, in a 

 potato field near Geneva, a tuber bearing a few 

 sclerotia of Ehizoctonia. The following day the 

 field was revisited and carefullv searched. The 

 crop had been harvested several days earlier, and 

 in the interval rain had washed the dirt from 

 such tubers as had been overlooked and also from 

 the stems of the plants which were left in the 

 field. This facilitated the search and we soon 

 gathered about 30 tubei's bearing sclerotia. See 

 Fio^. 20. Then we beo-an lookino: for sclerotia 

 on the stems and had little difficulty in collecting 

 about 25 good specimens. One of these is shown 

 in Fig;. 21. Havino* once seen the sclerotia on the 

 tubers it was easy to find them on almost every 

 lot of tubers examined. We found them, often- 

 times in great abundance, on tubers offered for 

 sale at the groceries in Geneva, Poughkeepsie and Ithaca. A 

 wagon load of potatoes offered for sale at Ithaca was so completely 

 overrun with JRliizoctonia that it is doubtful if there could have 

 been found in the entire load a single tuber which did not bear one 

 or more sclerotia. Some of the tubers showed several hundred 

 sclerotia each. These tubers were of the variety Rural New" Yorker 

 •No. 2 ; and in other respects they were fine, being of large size and 

 almost entii-ely free from scab and rot. They were grown at Slater- 

 ville, near Ithaca. A load of potatoes on the streets of Sayre, 



21. — Rhizoctonia 

 sclerotia on a potato 

 stem. {Natural 

 size.) 



