AUTOBASIDIOMYCETES 



449 



within the pith. The sclerotia, which are formed upon the surface 

 of the potatoes, do not seem to produce, in any case, rotting of the 

 tissues below. They are closely adherent, but merely superficial, and 

 perhaps serve particularly for the distribution of the fungus. 



Upon the sugar beet this fungus produces, besides the damping- 

 off already referred to, a characteristic form of rot. The leaves are 

 affected at the bases, and these promptly wilt and decay. The fun- 

 gus gains strength and penetrates into the superficial layers of the 

 beet root, and frequently causes serious rotting, accompanied by 

 cracking, as shown in Fig. 220. 



In Europe Rhizoctonia Medicaginis has been found upon the 

 beet, but that is a fungus very different from the Corticium, as 

 subsequently mentioned. Moreover, Rhizoctonia Medicaginis has 

 not been found in this country, although its hosts are such com- 

 mon plants as the asparagus, alfalfa, and sugar beet. Some of the 

 various hosts upon which the forms of the Rhizoctonia allied to 

 Corticium vagum var. Solani have thus far been found in America 

 are as follows : 



Sugar beet, Beta vulgaris, 



Bean, Phaseolus vulgaris, 



Carrot, Daucus Carota, 



Cabbage and Cauliflower, Brassica oleracea, 



Cotton, Gossypium hirsutum, 



Lettuce, Lactuca sativa, 



Potato, Solatium tuberosum, 



Radish, Raphanus sativus, 



Sweet potato, Ipomcea Batatas, 



Pumpkin, Cucurbita Pepo, 



Watermelon, Citrullus vulgaris, 



Garden pea, Pisum sativum, etc., 



as well as upon many species of ornamental plants and weeds. 



Upon the tomato plant this fungus attacks also the subterranean 

 parts of the stem and may be of importance where the soil is poorly 

 aerated. It may also occur upon the fruits when these are in con- 

 tact with the soil, but it is not probable that it becomes a fruit 

 disease except when fruit has been previously injured in some 

 manner. Upon either the potato or the tomato the fruiting stage 

 may develop upon the stems above the surface of the ground to 

 a distance of several inches. 



