USTILAGINALES 599 



vossia (Fig. 401) and Entyloma (Fig. 394, 8) and in the Graphiolaceae, 

 the spores arise singly and form a dusty mass at maturity. In Entyloma, 

 they remain in the interior of the host, joined into small, light-colored 

 nests which germinate in situ. In Sphacelotheca the spore fundaments 

 are only changed to real spores in the middle layers of the sorus; toward the 

 outside and the interior their formation is incomplete ; they remain color- 

 less, adhere in a tissue and form a five- to ten-celled hyaline sheath which 

 covers the true spores on both sides. 



In other genera, among the Ustilaginaceae, Tolyposporium, Theca- 

 phora, Testicularia and in the Tilletiaceae, Tuburcinia and Doassansia, 

 several or more spores are joined into a spore ball. In Tolyposporium, 

 Thecaphora and Tuburcinia (Fig. 400, 4 to 6), all spores are fertile. In 

 Fig. 402, 4, Doassansia (Fig. 403, 4 and 5, 9 to 11) the outer spores degen- 

 erate, lose their nuclei and contents and remain hyaline. In Testicularia 

 the spore ball consists of an outer fertile layer, surrounding an inner ball 

 of pseudoparenchyma. In Tuburcinia, the spore ball results from 

 repeated division of one or more cells from the same hypha; in Doassansia, 

 the whole hyphal tissue of an intercellular space or breathing pore 

 becomes changed to a large ball resembling a seed, whose outer cells 

 form an almost complete sheath, which, after the decay of the host 

 tissue, makes it possible for the ball to float on the surface of water. The 

 smut spores are generally disseminated by wind or insects; more seldom, 

 as in Doassansia, is the whole ball borne by water. They are mostly 

 capable of germination without a rest period but retain the ability to 

 infect for several years. Germination takes place in water, more freely 

 in dilute nutrient solutions; the exospore bursts open and a germ tube 

 whose wall is a continuation of the endospore protrudes. Germ pores 

 are known in only a few forms, e.g., Ustilago Tritici. The further course 

 of germination is used to separate the Ustilaginaceae and the Tilletiaceae. 



Ustilaginaceae. — Typical examples are Ustilago Scabiosae (Harper, 

 1898), U. Tragopogojiis-pratensis (Dangeard, 1892; Federley, 1904; 

 Rawitscher, 1912), U. violacea (Dangeard, 1892; Harper, 1898; Werth 

 and Ludwigs, 1912), U. Zeae (Rawitscher, 1912), Sphacelotheca Hydropip- 

 eris (Brefeld, 1895), U. Heufleri on Erythronium americanum (Sartoris, 

 1924) and Testicularia Cyperi (Edgerton and Tims, 1926). When the 

 germ tube (promycelium) has attained about one-third its final length, 

 the diploid nucleus migrates into it (Fig. 395); when the promycelium 

 is fully developed, it divides meiotically, forming three septa. In rarer 

 cases the nucleus remains in the spore and divides there; in this case one 

 daughter nucleus migrates to the promycelium, divides and a septum is 

 formed between the promycelial nuclei. The distal promycelial cell 

 may divide again, producing a three-celled promycelium. In contrast to 

 the basidium of the Auricularia type, the promycelial nuclei do not slip 

 out into the basidiospores but remain in the promycelium. By lateral 



