146 A TEXT-BOOK OF BOTANY 
fertilization, however, a structure called the spore-fruit is 
developed. These spore-fruits appear on infected leaves as 
minute dark dots (Fig. 134), each one being a sphere of 
heavy-walled cells (Fig. 135, 
B), which usually bear hair- 
like appendages of various 
forms. In fact, the spore- 
fruit is a heavy protecting 
case for spores, and carries 
mildews through the winter 
or the dry season. The ap- 
pearance of a many-celled 
spore-case as the result of 
fertilization, rather than a 
new mycelium, suggests the 
similar result of fertilization 
among the red Alge (§ 75). 
By bursting the wall of 
Fie. 135.—Reproduction of mildew: this spore-fruit, one or more 
4, chain of spores developed bY® delicate bladder-like sacs are 
sporophore; B, spore-case burst, 
and showing the extruded sac extruded, and through the 
{ascus) with its spores. — After 
aera nih: transparent wall of each sac 
several spores may be seen 
(Fig. 135, B). The delicate sacs are called asezv (singular, 
ascus),a word meaning “sacs,’’ and hence the great group 
of Fungi represented here by the mildews is named the 
Ascomycetes, which means ‘‘sac Fungi.” In the life-history 
of the mildews it is evident that there are two kinds of 
asexual spores: those produced in chains by the sporophores, 
and those produced in the sacs of the spore-fruit. Both 
produce new mycelia, the latter starting the first mycelia 
of the growing season, and the former multiplying mycelia 
throughout the growing season. 
83. Other Sac Fungi.—The group of sac Fungi is a very 
large one, containing many forms that are well known and 
