556 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



on dry rot of the white potato has also met with the fungus 

 Colletotrichttm atramentariiim, as he says: "It is common to find 

 associated with the Fusarium and likewise penetrating the tuber, 

 sometimes to a depth of one-fourth to one-half inch, a fungus 

 of the genus Vermicularia. . . . The Vermicidaria was present 

 to an extent of 10.3 per cent, .... When used alone it brings 

 about no disease symptoms. If it assists any in bringing about 

 the disease, its work is that of a semi-parasite which follows the 

 openings made by Fusarium.'' It is very probable that Frank 

 (6) and Johnson (9) originally dealt with the dry rot caused by 

 several Fusaria, which were obscured and overrun by Col- 

 letotrichum atramentarium. The probability of the latter fungus 

 being a saprophyte is also admitted by O'Gara,^ who writes: 

 "I do not think that the Colletotrichum is a very active parasite." 

 It is safe to assume that Collet otrichtim atramentarium is a common 

 saprophytic soil organism. The writer has found it time and 

 again on dead and dying stems of white potato, especially if the 

 hills were fully mature. It is noteworthy to add that on dead 

 stems the sclerotia are larger than they are when found following 

 the silver scurf fungus {Spondylocladium atrovirens) or on partly 

 dying potato vines. However, when these larger sclerotia are 

 dropped on an agar medium, the resulting growth is identical with 

 Colletotrichum atramentarium. This would seem to indicate that 

 the organism is only at best a semi-parasite under certain climatic 

 conditions, since there must be some element in the living host 

 which is unfavorable to the fungus. It is also interesting to add 

 that the setae of the acervuli are much more abundant in pure 

 culture on an agar medium and on steamed potato vines than 

 they are found in nature. When found accompanying the silver 

 scurf fungus, the setae are almost wanting. Species of Colleto- 

 trichum, as a rule, are not known to produce sclerotia, nor to 

 reproduce by means of such bodies. Colletotrichum atramentarium , 

 however, is an exception, since, in the former, the sclerotia seem 

 even to be a more important phase of reproduction than are the 

 spores; the latter are formed only in young cultures and very 

 sparingly on the host. As the organism increases in age, spore 

 formation in pure culture is dispensed with, and an abundance of 

 sclerotia with or without setae are formed in layers of concentric 



' Correspondence dated August 17, 191 5. 



