USTILAGINE^. 319 



411. Immediately preceding the formation of spores 

 the hyphae give rise to many branches, which differ much in 

 appearance from the ordinary ones. This takes place in 

 those parts of the host plant where the spores are afterward 

 produced. These spore-forming hyphae are thicker than the 

 vegetative ones, and are more gelatinous ; they are more or 

 less granular, and they sometimes contain oil globules. 



412. The spores are formed in Tilletia caries by little 

 lateral branches budding out upon the spore-forming hyphae, 

 and acquiring a pear-shaped outline ; they become thicker 

 and more spherical, and each eventually secretes a dark, thick 

 wall (Fig. 224, k' and k). When mature, the spores become 

 free by the drying up of the attaching pedicel. In Ustilago 

 the spore-forming hyphae break up their contents into 

 spores, and in some cases as, for example, in Ustilago 

 Maydis the process much resembles the formation of asco- 

 spores in asci (Fig. 221). It frequently happens that the 

 spore-forming hyphae fuse together on account of the gelat- 

 inous nature of their envelopes ; when this takes place, the 

 spores are formed in very irregular masses (Fig. 222, b). 



In Sorisporium Saponarm this fusing takes place to so 

 great an extent that the real nature of the process is greatly 

 obscured. The spore-forming hyphae, which are very abun- 

 dant, become curved at their extremities, and many of these 

 twist themselves into a little ball, and are fused into a single 

 gelatinous body, which eventually becomes a mass of spores. 

 The real nature of the spore-formation is probably indicated 

 by the "solitary spores," which appear singly upon those 

 spore-forming hyphae which do not compact themselves into 

 balls ; in these, the resemblance to asci containing single 

 ascospores is striking (Fig. 223). 



413. The spores, when ripe, have a double wall. The 

 outer the epispore is thick, usually brown or black, some- 

 times smooth, but frequently more or less rough by projec- 

 tions,-or marked by reticulations (Fig. 224, e). The inner 

 wall the endospore is a delicate colorless membrane, which 

 protrudes through the ruptured epispore in germination. 



414. The germination of the spores has been made out 



