478 



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 Corticium vagum 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 (R/ii- 

 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 

 vulgaris\ 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. 



Rhisoctonia Medicaginis does not occur 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 



