190 



THE ASCOMYCETES 



Species of Hvpomyces are of interest because they are parasitic 

 on various agarics and boletes. At times they are serious enemies 

 of mushroom culture, attacking the sporocarps in the button 

 stage and covering them with bright red or orange perithecia. 

 The ascospores are hvahne, two-celled, and fusiform. 



Folystigvm nibnnn causes a red-spot disease of Prunus, es- 

 pecially cherry, in Europe. Its development has been described 



Fig. 72. Volystigvia riihrinn. A. Basal portion of ascogonial coil, tricho- 



gyne not shown. B. Wall between two ascogonial cells partly absorbed. 



C. Complete plasmogamy. (After Nienburg.) 



by Blackman and Welsford (1912) and Nienburg (1914). In- 

 fections are initiated by ascospores. Five or six weeks later 

 bright-red stromata have formed ^\■ithin the leaves. Within these 

 stromata two types of conceptacles arise. One is flask-shaped 

 and bears slender, hooked spores that have been termed spermatia. 

 The other is filled with a loose tangle of hyphae, in which a 

 coiled, septate ascogonium is embedded. Filaments extend from 

 the ascogonium to the leaf surface. During damp weather in late 

 summer the spermatia ooze out in a slimy mass and adhere to 

 the trichogyne, but they have not been proved to function in 

 fertilization. Nienburg recorded the absorption of the wall be- 

 tween certain cells of the ascogonium, permitting a pair of sister 

 nuclei to be associated and plasmogamy to occur. Ascogenous 

 hyphae arise from this ascogonial cell. 



