8 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 
Figs. 27-55. These are protected more or less permanently 
by thin coverings of plant tissue, or in some genera, as Spha- 
celotheca, and often in Cintractia, by false membranes com- 
posed chiefly of fungous cells or threads, Fig. 5a. The sori 
vary greatly in size, sometimes forming outbreaks smaller 
than a pin-head, and sometimes, as often in corn smut, reach- 
ing several inches in diameter. Usually each species has a 
definite place on its host where the sori appear. This may be 
on the leaves, Fig. 35, on the stems, Fig. 28, in the blossoms 
as a whole, Fig. 54, or confined to the anthers, ovaries, Fig. 52, 
or seeds, Fig. 48. Occasionally a smut may break out in any of 
these places. In the grasses, when infecting the inflorescence, 
the sorus may be confined to the ovary, infest the spikelet as a 
whole, or even involve the entire inflorescence. Sometimes 
all of the ovaries or spikelets are infested and sometimes only 
part of them. The characters of the sori, of course, are modi- 
fied somewhat by the part of the host in which they develop, 
and also by the kind of host on which the smut occurs. 
Usually the sori are dusty and easily dissipated. With a few 
species they are hard, and the agglutinated spore mass is dis- 
seminated by gradual disintegration, often through the ab- 
sorption and loss of water. In these cases there is sometimes 
a gradual ripening of the spores from the outside of the sorus 
inward. With some genera (Entyloma, Doassansia, etc.) the 
sorus is rather permanently embedded in the tissues of the 
host, usually in the leaves, and often produces only a discolora- 
tion of these. The species of one of the European genera 
form gall-like growths in the roots. 
Germination of Spores. There are two chief types of 
germination of the Ustilaginee upon which the two families 
are based. In the Ustilaginacee, Fig. 21, the spores, when 
placed in a drop of water, send out a single, hyaline thread, 
several times their length, which usually divides into about 
four cells by cross partitions, or septa. This is called the 
promycelium. Usually at the apex of each cell one or more 
elongated thin-walled spores, or sporidia, are budded out, the 
apical cell bearing its sporidium terminally and the others lat- 
erally. The sporidia when full-sized are pinched off at the 
base, and others are sent out until the protoplasm of the cell 
