POWDERY MILDEWS 221 
cells below by cross partitions. The cells thus formed are 
at first oblong and cylindrical, with flattened ends; but 
the topmost ones soon become rounded at their extremi- 
ties, thus giving rise to a row of cells, the spores, or 
conidia. These fall off successively and germinate at once 
by pushing out a tube, which gives rise to a new plant. 
364. The sexual process (generation) in most species 
takes place late in the season. Two 7 
filaments crossing each other or coming 
into close contact swell slightly and send 
out from each a short branch; one of 
these becomes the oogone, and the other 
the antherid, both organs being very fic. 104,—Genera- 
much reduced. wench age ges 80 
365. Fertilization is effected by the direct union of 
protoplasm. Eight or ten branches then bud out below 
the oogone, and growing upward soon completely enclose 
it in a cellular coat which eventually becomes hardened 
and turns brownish in color, constituting the spore-fruit 
(perithecium). 
366. The oogone inside of the perithecium gives rise, 
by branching, to one or more large cells (young asc?) 
filled at first with granular protoplasm, which soon forms 
two to eight spores (ascospores). Upon its outer surface 
the spore-fruit develops long filaments (known as 
“‘appendages’’), probably for holdfasts. In some genera 
these terminate in hooks; in others they are dichotom- 
ously branched; in still others, needle-shaped; while in 
many species they end irregularly. The spore-fruits re- 
main during the winter upon the fallen and decaying 
leaves, and finally, by rupturing, permit the asci, with 
the contained spores, to escape. 
367. The Herbarium-mold (Aspergillus) is related to 
the Mildews and belongs to the order of Little Tubers 
