54 EVOLUTION OF PLANTS 
9, C, an), and closely resemble the zodspores except in 
size, and the partial or complete loss of chlorophyll. The 
spermatozoid has a large nucleus with relatively little 
cytoplasm, as the nucleus is probably of the most impor- 
tance in the act of fecundation. 
At maturity the odgonium opens and permits the en- 
trance of the motile spermatozoid, which at once pene- 
trates into the egg-cell where its nucleus fuses with 
that of the egg, 
thus fertilizing it. 
As the result of 
fertilization the 
egg becomes in- 
vested with a 
heavy cell-wall and 
forms a resting- 
spore which  re- 
mains dormant for 
a long period, and 
is capable of re- 
sisting, unharmed, 
Fic. 10.—A, a plant of Coleochwxte scutata, freezingand drying 
one of the highest of the Confervacee; B, 
beeen of another species, C. pulvinata, UPp- 
with an odgonium, og; C, the germinating ‘ : 
ee seen = section, ‘showing its ainsi In the highest 
into a nearly globular cell-mass; each cel 5 
later gives rise to a single Diciliate zoospore. typ e of all, repre 
(Figs. B and C after Oltmanns.) sented by the pecu- 
liar genus Coleo- 
chete (Fig. 10), the odgonium, with the contained 
odspore, becomes, after fertilization, invested with a 
protective covering formed by the growth of adjacent 
cells, so that the influence of the act of fertilization ex- 
tends beyond the egg-cell. Coleochete, as we shall see 
