Some Saprophytic Fungi 'of Potatoes. G. H. Pethyhridge. 115 



in these media as freely and abundantly as pn decaying tubers 

 under natural conditions. 



The form and structure of the perithecia have been described 

 in detail by Reinke and Berthold, and there is little to be added 

 in this connexion. When ripe the ascospores are expressed 

 through the mouth of the perithecium in the form of a yellow 

 mass. Perithecia with two necks have occasionally been 

 observed in naturally growing material but they were not seen 

 in any of the cultures. 



Inoculation Experiments. Healthy living potato stalks,, 

 tubers and rhizomes were inoculated at various times and 

 repeatedly with ascospores, conidia and mycelium bearing 

 both conidia and chlamydospores, but no infection occurred 

 in any single case and no rot was set up. Hypomyces Solani, 

 therefore, is a saprophyte which in addition to its perithecial 

 stage produces conidia and chlamydospores resembling in some 

 respects those produced by certain species of Fusarium. There 

 are, however, pronounced differences between typical species 

 of Fusarium and the conidial stage of Hypomyces, and it is 

 concluded that H. Solani is not the perithecial stage of Fusarium 

 Solani or of any other species of Fusarium. 



IV. TWO NEW SPECIES OF VERTICILLIUM. 



In a previous paper* dealing with the disease of the potato 

 plant caused by Verticilliuni albo-atrum R. et B. attention was 

 called to the discovery of two new species of Verticilliuni, 

 occurring on the surface of potato tubers, which, in the absence 

 of infection experiments or study in cultures, might easily be 

 mistaken for V. albo-atrum. Indeed, it seems not at all unlikely 

 that it was the presence of one or the other of these species on 

 the surface of the tuber which led Berthold and Reinke into the 

 error of supposing that V. albo-atrum did not actually enter 

 the tuber, as it has now been proved to do, but reached the 

 developing sprouts from without, after having traversed the 

 outer surface of the tuber. A brief description of these two 

 species seems, therefore, desirable. 



One of them, which it is proposed to call V. nubilum, M^as 

 found at a spot on the surface of a tuber attacked by Phyto- 

 phthora i^tfestans where the skin had received a slight mechanical 

 injury; the other, V. nigrescens, on the skin of a tiiber affected 

 with ordinary "scab." Both were obtained in pure culture, 

 starting from a single conidium in each case, and both were 

 grown on a large number of different solid and liquid media 



* Pethybridge, G. H. The Verticillium Disease of the Potato. Sci.Proc. 

 Roy. Dubhn Soc. xv. (N.S.), No. 7, 1916, p. 75. 



