No. 5.] USTILAGINEE 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 promyceliurn, 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 Tilletiacee, 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 aérial 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 
