xx.] GRASS MILDEW. 133 



enlarged 100 diameters. When they burst the contained 

 bladders or asci often burst at the same time, and the 

 living sporidia, after their six months' rest, fly into the air. 

 At other times the bladders or asci themselves fly out of 

 the perithecia, and sail, each with its little load of eight 

 sporidia, through the air. When in the air the asci or 

 bladders burst, and the spores are set free in the atmos- 

 phere. The facts just given can easily be seen when old 

 grass or straw infected with Erysiphe is kept in damp air 



FIG. 61. 



Concoptacle of Erysiphe graminis, "D.C., bursting in spring. 

 Enlarged 100 diameters. 



under a bell-glass, if strips of glass smeared with glycerine 

 are suspended over the infected leaves. On to these 

 strips of glass the asci and sporidia will be ejected from 

 the perithecia. It is a curious fact that the little sporidia 

 are so ready for germination in the spring that they com- 

 monly burst and produce spawn threads as they sail 

 about in the air. 



Such of the sporidia as alight on the Gramine or 

 grasses attach themselves to their hosts by their spawn 

 threads, and speedily produce a necklace-like Oidium 



