Ch. X] 



THE BLACK FUNGI 



453 



inclosing some bark tissue, it forms the black, compact, 

 rounded, swollen masses (sclerotium), which everybody 

 knows. From the surface rise short stalks wherefrom 

 conidia (spores) are abstricted and carried by the wind to 

 infect other trees. In autumn small papilla-like perithecia, 



Fig. 316. — The Ergot Fungus, Claviceps purpurea. 



Left, ear of Rye, with projecting sclerotia, natural size. Next, above, 

 section through a sclerotium, showing the compact pseudo-parenchymatous 

 mycelium, X 250 ; below, sclerotium, with fructifications, X 3, and one 

 of the latter in section, showing perithecia, X 20. Next, a perithecium, 

 showing asci, X 200, and a single ascus, with the filamentous ascospores, 

 X 350. Below, the hypha, which develops from an ascospofe on the 

 grain, bearing conidia. (From Strasburger.) 



containing 8-spored asci, form also on the surface, and in 

 the spring the spores escape and are disseminated by wind. 

 Another prominent form is the Ergot of Rye and other 

 grasses (Fig. 316). The ascospores, in early summer, infect 

 the ovaries of rye flowers, causing them to swell ; and the 

 mycelium later develops conidia from short stalks on the 

 surface of the grain. At the same time the mycelium 



