Family Agaricaceae 105 



United States is as yet unknown. However, if once 

 introduced in a cave, it is likely to ruin the entire 

 crop. 



Symptoms. The symptoms of the disease are often 

 various. The presence of the malady may be indi- 

 cated by small tubercules on the cap and by a form 

 of fluffy white growth on the gills, which interferes 

 with their normal development (fig. 18). The result 

 is distorted caps and stipes and finally a general 

 darkening and decay of the tissue. In severe cases 

 monstrous soft masses with thick white fungus coat- 

 ings are observed in houses in which the disease is 

 very prevalent. In this case the affected plants have 

 little resemblance to mushrooms. They decay rap- 

 idly, and emit a very disagreeable odor. 



The Organism. The spores of Mycogone perniciosa 

 are very characteristic. They consist of two cells, the 

 upper spherical, rough, and covered with warts, the 

 lower hyaline, smooth. Both cells possess a thick wall. 



Control. According to Veihmeyer, 1 there are no 

 evidences that tend to show that the Mycogone 

 disease is carried with the spawn manufactured by the 

 "tissue culture" method. It is very probable, how- 

 ever, that the disease was introduced into this coun- 

 try from France with imported virgin spawn 

 collected at random from fields. The disease may be 

 introduced into a new place with the manure and 

 then spread quickly in a number of ways. Immedi- 

 ate temporary measures are essential for the control 

 of this trouble. Diseased plants when first noticed 



1 Veihmeyer, F. J., U. S. Dept. of Agr. Bui. 127 : 1-24, 1914. 



