208 



Bulletin 132. 



all parts of the leaf, and by careful observation they may be seen 

 with the naked eye. 



A section of a leaf through one of these minute pycnidia is 

 shown in Figure 52. At a is shown a cross section of the more 

 or less spherical fruit body. It is deeply immersed in the tissues 

 of the leaf, and the walls are stout and appressed. From these 

 walls arise a forest-like mass of minute filaments, or basidia, 



51 — Spots of late blight on a celery leaf. 



bearing the needle-shaped spores, or reproductive bodies of the 

 fungus. When ripe, these spores are doubtless expelled through 

 the mouth of the pycnidium by means of absorbed water, and 

 then they are readily scattered by wind and rain for the immediate 

 dissemination of the fungus. The spores readily germinate, giv- 

 ing rise to the delicate tube-like filaments, which enter the tissues 

 of the leaf as mentioned for the Cercospora. 



