THE FUNGI 
91 
arrangement; but in all the higher ones they are borne in 
definite spore-fruits of characteristic form. 
This spore- 
fruit is undoubtedly, in many instances, the result of 
fertilization, being pro- 
duced by the formation of 
a peculiar cell, the archi- 
carp, which corresponds to 
the odgonium of the Phy- 
comycetes. This is usually 
fertilized by direct contact 
with the antheridium, and 
from it, more or less di- 
rectly, are produced the 
spore-sacs or asci. 
A good example of these 
simpler Ascomycetes is 
offered by the mildews 
which infest many plants, 
e.g. Spherotheca, the com- 
mon rose mildew. These 
are true parasites, but grow 
entirely upon the surface of 
the host, into whose epider- 
mal cells are sent suckers 
by means of which the 
parasite obtains nutriment 
from the host. The myce- 
lium of the fungus sends 
up vertical branches from 
Fic. 24 (Ascomycetes).— A, a chain 
of conidia or non-sexual spores of 
a mildew (Spherotheca), one of 
the simpler sac-fungi, or Ascomy- 
cetes, growing upon the leaves of 
the dandelion; B, the sexual repro- 
ductive organs, archicarp, ar, and 
antheridium, an; as the result of 
the fusion of these there is formed 
the spore-fruit, C, containing the 
single spore-sac, or ascus, sp, which 
is derived directly from the fertil- 
izer archicarp; D, the ripe spore- 
fruit seen from without; E, a 
single spore-sac containing eight 
spores; F, a cup-fungus (Ascobo- 
lus) ; G, section of the spore-fruit 
of Ascobolus showing the numer- 
ous spore-sacs, which are also 
derived from a fertilized archicarp; 
H, a single ascus of Ascobolus. 
which are successively cut off oval cells — spores or 
“conidia,” — which germinate promptly and through 
whose means the fungus may spread rapidly. 
