NO. 5.] USTILAGINE^E OF CONNECTICUT. 9 



is exhausted. These sporidia germinate by a short slender 

 thread (infection thread) that usually pushes out from near 

 one end, Fig. 24. In some species the cells of the promyce- 

 lium, instead of forming the sporidia, give rise directly to the 

 infection threads, Fig. 23. Sometimes the adjacent cells of the 

 promycelium become connected by closely applied short 

 threads, forming buckle or knee joints, and from these may 

 develop infection threads. Some species germinate directly 

 into elongated threads which scarcely partake of the nature of 

 a promycelium. When nutrient is added to the drop of 

 water, the spores germinate much more luxuriantly, the spor- 

 idia usually sprouting out other sporidia while still attached 

 to the promycelium. Especially in a solid cultural medium 

 these chains develop a more or less complicated system of 

 branching, Fig. 25. In a liquid solution, the sporidia usually 

 soon fall off from the promycelium, but continue to multiply 

 by the yeast fashions of budding new sporidia, which soon sep- 

 arate and develop others, until the nourishment is exhausted. 

 Then the sporidia may develop infection threads. 



The second chief type of germination is shown by the spe- 

 cies of Tillctiacccc, Fig. 22. The simple or septate promyce- 

 lium in this case bears all of the elongated sporidia in a terminal 

 cluster. Sometimes these primary sporidia develop terminal 

 secondary sporidia. With some species the sporidia, before 

 or after falling off from the promycelium, become yoked in 

 pairs by short connecting threads. In nutrient solutions some 

 of the species develop finally a complicated mycelium that 

 bears numerous aerial sporidia or conidia quite different from 

 the normal type produced in water. The conidia develop in- 

 fection threads on germination. 



Infection of Host. The host is entered by the fine infec- 

 tion threads of the promycelia or the sporidia boring through 

 its tissues into the interior. Once inside, these develop the 

 mycelium of which we have already spoken. Many of the 

 smuts infect their host only through the young hypocotyl or 

 epicotyl of the seedling. In these cases the smut usually can 

 not gain successful entrance after the plants appear above 

 ground. Once inside, the mycelium rapidly penetrates the 

 young tissues, seeking to gain access to the growing tip, where 



