i New York Agricultural Experiment Station. Ill 



On August 3 while peeling some scabby potatces for potato 

 agar we observed that some of the so called '' deep scab " ulcers 

 were filled with mycelium composed of rather coarse hypha?. 

 Microscopic examination showed the hyphse to be those of 

 Rhizoctonia. 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 that Rhizoctonia hyphae are of frequent occurrence 

 in scab ulcers. 



The next advance made was the discovery of the Rhizoctonia 

 sclerotia on the tubers and stems. On September 21 Mr. Rolfs 

 found, in a potato field near Geneva, a tuber bearing a few 

 sclerlotia of Rhizootonia. The following day the field was re- 

 visited and carefully 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 tubers bearing sclero- 

 tia. See Fig. 5. Then we began looking for sclerotia on the 

 stems and had little difficulty in collecting about 25 good speci- 

 mens. One of these is shown in Fig. 6. Having once seen the 

 sclerotia on the tubers it was easy to find them on almost every 

 lot of tubers examined. We found them, oftentimes 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 Rhizoctonia 

 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 

 entirely free from scab and rot. They were grown at Slaterville, 

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

 was examined and found to contain a considerable number of 

 tubers bearing sclerotia. We have also seen the sclerotia on 

 tubers grown at Mattituck and Cutchogue. Mr. A. D. Selby has 



