FUNGOUS DISEASES OF PLANTS 



and wild plants. The last-mentioned fungi are at least closely 

 related, perhaps forms of a single species ; and in this treatise 

 they are provisionally referred to the genus Corticium. They have 

 been discussed under Corticinm vagnm B. & C., var. Solani Burt. 



The writer examined various 

 diseases due to Rhizoctonia 

 while in Europe during 1899 

 and 1900, and subsequently 

 in the United States. As a 

 result, certain observations 

 may be stated. In the first 

 place, the common alfalfa 

 root fungus of Europe (Rhi- 

 zoctonia Medicaginis) is the 

 same as the European root 

 fungus of asparagus (Aspara- 

 gus officinalis]. This species 

 also occurs less frequently 

 upon the sugar beet (Beta 

 I'ulgaris), and, doubtless, 

 upon other cultivated and 

 wild plants. The fungus ap- 

 pears upon the root as a close 

 weft of violet-colored hyphae 

 (Fig. 239), composed of cells 

 more or less uniform in diam- 

 eter, filamentous, branched, 

 but without a particularly 

 characteristic type of branch- 

 ing. Morphologically, it 

 bears no resemblance to the 

 sterile stage of Corticium 

 vagum, above referred to, 

 that is, the form causing the rot of the crocus, and a similar disease 

 of the carrot, etc., in Europe, the rot of beets, stem rot of carna- 

 tions, certain damping-off diseases, etc., in America. 



Rhizoctonia Medicaginis is not common in America so far as 

 can be ascertained. In Europe it is one of the most destructive 



FIG. 239. RHIZOCTONIA MEDICAGINIS ON 

 ROOTS OF ASPARAGUS 



