268 STEUCTURE AND LIFE HISTORIES 



A SAC-FUNGUS (MICRO SEHiERA) 



260. Habitat and Structure. — The fungus, Micro- 

 sphcera, may be found growing on the leaves of the lilac, 

 and is commonly called "powdery mildew." The my- 



FiG. 193. — ^Lilac mildew {Microspara Alni). The white areas are the 

 mycelia of the fungus, growing over the surface of the leaf. The tiny 

 black dots are the perithecia, which contain the asci. 



celium is septate, and forms a web over the surface of the 

 leaf (Fig. 193), sending down haustoria into the epidermal 

 cells, to secure nourishment, and sending up short branches 

 (conidiophores) , each bearing a chain of colorless spores 

 {conidid) . 



