10161 



DUGGAR RJIIZOCTONIA CROCORUM AND R. SOLANI 407 



made the starting point for mycological nomenclature, that 

 he designates three species in the following order, (1) R. 

 Crocorum DC, (2) R. Medicaginis DC, and (3) R. muscorum 

 Fr., also giving R. Mali DC among species ignota. The 

 descriptions of the two species first mentioned leave no doubt 

 that he is here defining the violet root felt fungus of crocus 

 and of alfalfa. Moreover, Fries recognized Sclerotium Cro- 

 corum Pers. as a synonym of R. Crocorum DC So far as has 

 been ascertained no specimens of these species which he ex- 

 amined are still in existence. Link (1824) excluded the doubt- 

 ful forms, added a species R. strobilina, and otherwise left 

 the genus as constituted by De Candolle. Duby (1830) in- 

 cluded among the species Rhizoctonia Allii Graves, arranging 

 the genus close to Sclerotium in the Scleroteae of Lycoper- 

 claceae. Fries later included in this genus R. Batatas Fr. on 

 Ipomoea Batatas from America. 



The most complete mycological account of the genus Rhizoc- 

 tonia is that given by L. and C Tulasne ( '62). They reduce 

 R. Crocorum DC and R. Medicaginis DC to a single species 

 to which they apply a new name, significant of the appearance 

 of the fungus, R. violacea Tul. This reduction to a single form 

 was made after a most careful morphological study of the 

 fungus in all stages. From the accurate descriptions and the 

 excellent illustrations it is clear that they had under con- 

 sideration material referable to the names above. The Tulasne 

 brothers also refer to other species insufficiently known, as 

 follows: R. Allii Graves, R. Batatas Fr., and R. (?) Mali DC 



« 



They were inclined to the view that the affinities of the genus 

 would be found to be with the Ascomycetes, and, in fact, they 

 considered certain minute cushions of hyphae, referred to in 

 detail later, as immature perithecia. Successively, therefore, 

 attention was drawn by mycologists (1) to the sclerotium as a 

 fruit body (Du Hamel and Bulliard), (2) to the sclerotium 

 as a sterile structure (Persoon), (3) to the strand-like habit of 

 the mycelium (De Candolle), and (4) to the minute cushion- 

 like sclerotia as suggesting perithecia (Tulasne, L. and C). 



