TAUBENHAUS: SILVER SCURF OF THE WHITE POTATO 555 



in water and the liquid used for inoculation. In order to determine 

 definitely the pathogenicity of Spondylocladium atrovirens, spores 

 from a pure culture of the latter were suspended in sterile water 

 and sprayed on healthy white potatoes. Before inoculation 

 these tubers were washed and disinfected for ten minutes in a 

 solution of 5 parts of formaldehyde in 95 of water. They were 

 then kept two weeks in sterile moist chambers to see if any disease 

 would appear. In making microscopic mounts twenty-four hours 

 after infection, the spores of Spondylocladium atrovirens were seen 

 to germinate (figs. 27, 28, and 29) and to break through the 

 epidermis (fig. 26). This agrees with the observations of Appel 

 and Laubert (11). In about two to four weeks, typical spots of 

 silver scurf appeared. This was repeated several times with the 

 same results. The symptoms of the artificial infection were 

 identical with those seen in nature, with the exception, however, 

 that the sclerotia of Colletotrichum atramentarium were absent. 



A series of inoculations was also carried out with spores from 

 fresh cultures of Colletotrichum atramentarium. At no time did 

 infection appear. Inoculations were also made by inserting bits 

 of mycelium and sclerotia of the above fungus into slits made in 

 the epidermis of the tuber. In no case did infection appear. 

 This clearly shows that Spondylocladium atrovirens Harz and not 

 Colletotrichum atramentarium (Berk. & Br.) Taub. is the cause of 

 silver scurf. Nevertheless, and as previously pointed out, Frank 

 (6) and Johnson (9) recognize a form of dry rot due to Colleto- 

 trichum atramentarium. The writer agrees with Appel and 

 Laubert (11) that the dry rot of Frank and of Johnson above men- 

 tioned was probably caused by another organism, perhaps 

 Fusarium. It has already been pointed out that Halsted (3) did 

 not consider Colletotrichum atramentarium, to be the cause of the 

 stem wilt of white potatoes which he studied. Stewart (4) in 

 working with an apparently similar stem blight of potatoes 

 attributes the probable cause to Oospora rosea (Preuss.) Sacc. & 

 Vogel, or to Melanospora ornata Zukal. Stewart could not find 

 the association of Colletotrichum atramentarium with his stem 

 blight, as previously noted by Halsted. It is very probable that 

 both Halsted and Stewart were then dealing with a stem blight 

 caused by some species of Fusarium. Dr. Manns^ (18) in his work 



^ Dr. Manns has pronounced his Vermicularia identical with Colletotrichum atra- 

 mentarium (Berk. & Br.) Taub. 



