F. J. F. SHAW. 14") 



sclerotia, hut tliei'e is no luc'iitioii of microsclerotia in his paper. It 

 is difficult to understand therefore on what grounds the American 

 Rhizoctonia on potato can be identified as R. SoJani Kiihn. If botli 

 these sclerotia really belong to one fungus, then the creation of /'. 

 riolacea Tul. as a collective species, possibly including R. Solan I 

 Kiihn, would be justified ; the evidence contained in this paper, 

 however, is decidedly against this view. Cultures and inoculations 

 of the microsclerotia always gave microsclerotia, cultures and 

 inoculations of macrosclerotia either produced macrosclerotia 

 or the fertile Corticimn stage. Additional evidence showing that 

 the two sclerotia are really distinct is furnished by the work of 

 Stevens and Hall and of Eriksson. 



Stevens and Hall (26) describe macrosclerotia in association with 

 the Cortici urn stage on the apple, but they do not make any mention 

 of microsclerotia. Again, judging from the description and figures 

 in Eriksson's paper, the fungus on carrot, which he considered to be 

 R. violacea, possessed typical Rhizoctonia hyphse and the small 

 blackish brown microsclerotia, but here again there is no mention of 

 macrosclerotia. Thus in two cases investigators working with one 

 form have failed to mention the other, a fact which is hardly credible 

 if the original conception of R. violacea is correct. In some cases 

 (e.g., ground nut and cow pea) both forms may occur on the same 

 host, and indeed it was their association on the saffron which led 

 Tulasne to attribute them to one fungus. 



Assuming that two distinct fungi are present, and that the spe- 

 cies R. violacea Tub, like many other botanical species, is a com- 

 posite one, the c^uestion of the identity of the macrosclerotial 

 form with any known species of Rhizoctonia remains to be settled. 

 Certain points of resemblance were noticed between this form and 

 R. destruens Tassi, which occurs on the roots of Delphiniitm in Italy, 

 otherwise none of the known species seem to resemble it very closely. 

 On the whole, perhaps the simplest and most convenient solution of 

 the difficulty would be to retain the name R. violacea for the macro- 

 sclerotial form. While, therefore, the fertile stage of the macro- 

 sclerotial form is Corticiiim vagum, that of the microsclerotial, which 



