MOSSES 179 
It must be remembered, however, that the sperms are very 
small and can swim in such a film of water as may be left 
on the plant by a heavy 
dew orrain. Since many 
mosses grow in very dry 
places, fertilization with 
them must be very in- 
frequent. When the 
sperms are free to swim 
they are attracted toward 
the necks of the arche- 
gonia, Pass down them, Fre. 174.—Spore-cases of a moss, from which 
reach the egg, and fertili- the lids have fallen, displaying the teeth. 
zation is accomplished. Gisabidcta 
The odspore thus formed within the archegonium at 
once begins to germinate (Fig. 172), and forms the spore- 
producing structure, which in mosses is much more than a 
Fig. 175.—Filamentous growth of the young moss: A, very young filament coming 
from a spore (s); B, older filament, showing branching habit, remains of old 
spore (s), rhizoids (r), and buds (b) which develop the erect leafy branches.— 
After MUELLER-THURGAU. 
