May 15, 191S Seedling Diseases of Sugar Beets 1 53 



R. violacea into artificial culture have thus far failed, though many 

 different workers have undertaken it. So far as can be determined from 

 the literature, the American fungus also appears to be identical with 

 Shaw's (42) Corii-cimn vagum B. and C, and it is indistinguishable in 

 culture from a strain isolated in Ireland by Pethybridge from a single 

 spore of Hypochnus on the potato, and kindly contributed by him under 

 the name " Hypochnus solani." 



The fungus is characterized by a septate mycelium the branches of 

 which in young cultures are either parallel to or inclined at a more or 

 less acute angle to the direction of growth of the parent branch. There 

 is a constriction where the branch unites with the old hypha and a 

 septum is formed a few microns from the point of origin. The threads 

 are hyaline when young, becoming a yellowish brown with age. In 

 mature cultures the branches are usually arranged very nearly at right 

 angles to the parent thread at the point of origin. In culture and less 

 frequently upon the host it forms sclerotia, which vary greatly in size 

 (PI. XX, fig. 2). One shown in the illustration of a sugar beet measured 

 a full half- inch (Pi. XXIII). They are usually much smaller, from i to 

 3 mm., and those produced in cultures are likely to be quite irregular in 

 outline. The sclerotia consist of interwoven branches, forming a loose 

 pseudoparenchyma of uniform structure throughout. The sclerotial 

 hyphae are broken up into short cells each of which may function as a 

 spore when placed under favorable conditions for development. The 

 Corticium stage has not been obser\'ed upon the sugar beet, but the 

 fungus appears to be identical with the form on the potato and a variety 

 of other plants upon which the Corticium is common, and the name 

 "Corticium vagum B. and C, var. solani Burt.," which is the one most 

 generally accepted in America, is being retained for the purposes of this 

 paper. 



The beet diseases produced by this fungus in America are unknown in 

 Europe, and this fact has been used as an argument that they can not 

 be correctly attributed here to the fungus which produces the sclerotia 

 on potatoes there. This argument is fully met, however, when we 

 approach a study of the environmental factors upon which the fungus is 

 dependent for the production of disease, since the climatic and soil 

 factors under which it becomes an active parasite in some portions of 

 America are not found in Europe. 



INOCULATION EXPERIMENTS ON BEET SEEDLINGS 



The 34 cultures used in the inoculation experiments on seedlings were 

 obtained from the following sources : 



Sugar-beet seedlings grown in the field at Rocky Ford, Colo., 5; at 

 Madison, Wis., in Rocky Ford soil, 5; at Madison in Garden City, Kans., 

 soil, 2; at Washington in greenhouse soil, 3; in sterilized soil infected 

 with decayed beets, 2; in Madison greenhouse soil, i; at Madison in 



