THE MYCOGONE DISEASE OF MUSHROOMS AND ITS CONTROL. 7 



cultures from inoculations made indiscriminately from the common 

 and sclerodermalike forms. Further investigation, however, may 

 demonstrate the occurrence of this small conidial form. 



Figure 2 illustrates the Mycogone stage of the disease. During the 

 course of the present investigation many hundreds of cultures were 

 made, both from infected material and by transfers from pure cul- 

 tures of the fungus. With few exceptions, spores of Verticillium 

 developed first and later were followed by Mycogone. The spores of 

 Verticillium are hyaline, oblong cylindrical, and borne on tapering 

 branches. They are generally one celled, but occasionally larger, 

 2-celled spores are developed. They are variable in size, the aver- 

 age measurement being 20 by 3.5 // for the larger 2-celled spores. The 

 cell wall is uniformly thin. Often, as noted by Costantin and Dufour 



Fig. 1.— Irregular mass of a diseased mushroom growing among normal mushrooms. 



(1892c) and Prillieux (1897), these Verticillium spores were borne on 

 the same hyphse as the Mycogone spores. The Mycogone spores were 

 usually produced at the bases of the hyphas strands and the Verticil- 

 lium spores at the apexes. 



Figure 2 is an illustration of the Mycogone spores and the manner 

 in which they are produced on the mycelium. They are two celled, 

 the upper cell spherical and rough or covered with warts. At first, 

 both cells are hyaline or colorless; later, the upper cell becomes light 

 brown, the lower cell usually remaining hyaline, but in rare cases 

 becoming faintly tinged with brown, averaging in size from 20 to 

 30 fi. The cell walls are thick, while the spores of the Verticillium 

 possess very thin walls. 



