312 



THE FUNGI WHICH CAUSE PLANT DISEASE 



and the mycelium there develops richly under the epidermis. The 



outer cells remain sterile and constitute the membrane; the inner 



gelatinize and develop into spores. 

 S. reiliana (Kiihn) Cl.^* "'^ ^^ '*" ^^ 



Sori very prominent forming irregular masses including more or 

 less of the entire panicle, usually 

 5-15 cm. in length; often at first pro- 

 tected by the leaf-sheath. A whitish 

 false membrane encloses the black- 

 brown spore-mass and the ray-like re- 

 mains of the j)eduncles or columellas. 

 In time it becomes ruptured and the 

 spores scattered. Sterile cells are also 



Fig. 226.-S. reiliana. " Ger- Scattered in gToups through the spore- 

 mination in water. After. mass, chiefly subspherical, 7-15 fl in 



Hitchcock and Norton. ,. , i , 



diameter; spores somewhat opaque, 

 chiefly subspherical to spherical or occasionally ovoid or slightly 

 angled, minutely but abundantly verruculose, 9-14 /i in length. 



This is a cosmopolitan but comparatively rare form on com, 

 afEecting the ovaries. It occurs also on sorghum. In germination 

 a 3 to 4-celled, often branched, promycelium is formed and conidia 

 are produced. 



S. diplospora (E. & E.) CI. is found on Panicum crus-galli and 

 related grasses in the lower Mississippi Valley. 



Sorosporium Rudolphi (p. 302) 



Sori in various parts of the host, forming dusty, dark colored 

 spore-masses; spore-balls of medium size com- 

 posed of numerous fertile cells, often rather 

 loosely united and frequently at maturity com- 

 pletely separating; spores usup,lly olive or 

 reddish-brown, of medium size; germination 

 similar to that of Ustilago; sometimes with 

 elongate germ thread and no sporidia. 



Several species are parasitic on the coarser 

 range grasses. S. consanguineum E. & E., 

 S. everhartii Ell. & Gall., and S. ellisii Winter, are probably the 

 most important. S. dianthi Rab. is found on Dianthus. 



Fig. 227. — Sorospo- 

 rium. Spore mass. 

 After Dietel. 



