The Sterile Fungus Kiiizoctonia. 71 



the Rhizoctonia of lettuce. From the characters cf the parasitic 

 material, as well as from pure cultures, we considered it identical with 

 the damping-oif fungus. The specimens received shov'ed no rotting 

 of the stem, the leaves being the seat of attack. On the older 

 lower leaves the leaf blades alone are affected ; but the more deli- 

 cate inner leaves succumb entirely, blackening and decaying with 

 the progress of the disease. Hyphi^* of the fungus occurred 

 scantily over the leaf surface, and a short tufted growth might be 

 found on the inner side of the petioles. Tiiese tufts were brownish- 

 white or tawny in color and not so dark as the corresponding growth 

 in culture. 



During the past winter this fungus has also been found by Mr. 

 Kolfs on greenhouse lettuce plants at Rochester. 



Again, Atkinsonf found a form of the sterile fungus studied by 

 him in Alabama, causing damping off of lettuce seedlings at Ithaca. 



Occurring, then, in such widely separated regions it is very prob- 

 able that it is a fungus very generally distributed. 



On the Potato, Solantmi tuberosum. 



Although a Rhizoctonia;}: disease of potatoes has long been com- 

 mon in Europe, especially in Germany, where it is known under the 

 names " Grind " and " Pockenkrankheit," there is, so far as we are 

 able to ascertain, no record of the occurrence of IiMzoctonia on 

 the potato in America. Yet our observations indicate that potatoes 

 in the United States may be cpiite geilerally infested by a species of 

 Rhizoctonia^ as the subsequent discussion will demonstrate. 



The occurrence of this fungus upon potatoes was first brought to 

 our attention by Messrs. F. A. Sirrine and F. M. Polfs, who 

 reported having found it on potato stems collected in the vicinity 

 of Jamaica on Long Island. In the latter part of July the writers 

 visited Long Island and examined several potato fields in the 

 vicinity of Jamaica and Floral Park. A little RMzoctonia was 

 found on the potato stems in all of the fields examined, but it was 



* Compare Stone, G. E., and Smith, R. E.— The Rotting of Greenhouse Let- 

 tuce, Bulletin 69, Mass. Agl. Exp. Sta. (Hatch), p. 16-17, 1900. 

 f Atkinson, Geo. F. — 1. c. 

 % RMzoctonia solani, Ktihn. 



