THE FERNS 129 
phyte may be described as amphibious, inasmuch as it 
must become aquatic, so to speak, in order that fertili- 
zation may be effected. 
The spermatozoid, attracted by the substance ejected 
from the open archegonium, swims to it and makes its 
way through the 
canal in the neck 
to the central 
cavity, where it 
quickly —_pene- 
trates the egg- 
cell and slowly 
fuses with its 
nucleus, after 
undergoing a se- 
ries of changes. 
As a result of 
fertilization the 
egg begins to Fic. 33.— A, the open archegonium of the ostrich- 
grow, having 
in the mean 
time secreted a 
wall about itself, 
and thus forms 
what may be 
called a spore, 
fern, showing the egg-cell, 0, within the venter; 
B, the antheridium of the same species; C, a 
free spermatozoid, showing the numerous cilia; 
D, the fertilized archegoninm containing the 
young embryo sporophyte; E, the archegonium 
of a liverwort, Riccia, with the young sporophyte, 
showing the close resemblance between the ferns 
and mosses in regard to the young sporophyte ; 
F, longitudinal section of an older embryo of 
the ostrich fern, showing the division into stem, 
st; leaf, L; root, R; and foot, F. 
comparable to the resting-spore of such green alge as 
(Edogonium, or to the fertilized egg-cell in the moss 
archegonium. Like the latter it germinates at once 
instead of passing through a long dormant period, as in 
most green alge. 
The early divisions in the young embryo, developed 
K 
