MOSSES AND LIVERWORTS 105 
In the Archegoniates the structure arising from the 
fertilized egg is much more complicated than in any of 
the alge. Here, also, the egg after fertilization secretes 
a cell-wall about itself, but instead of remaining at rest 
for a long time, growth begins almost at once. The 
plant thus formed is entirely different from the one 
which produces the sexual organs, and the reproductive 
cells to which it gives rise differ entirely from those of 
the sexual plant. These cells are purely non-sexual in 
character and capable of germinating at once. They 
are spores which differ from the corresponding ones of 
the green alge in being destitute of ciliaand provided 
with a very firm membrane which enables them to resist 
extremes of temperature and dryness. 
The spores in all the Archegoniates are formed in 
groups of four from the division of a common mother- 
cell. The tissue from which the sporogenous cells arise 
is termed the “archesporium.” These spores on germi- 
nation give rise, not to another spore-bearing plant, 
but to the sexual one. This alternation of sexual and 
non-sexual individuals is a constant characteristic of the 
Archegoniates, and the two phases are known respec- 
tively as the gametophyte (sexual) and sporophyte 
(non-sexual), — convenient terms which will be adopted 
in the future discussion of the group. 
Among the lower Archegoniates, as in the alge, it 
is the gametophyte which is predominant and the spo- 
rophyte is small and inconspicuous, looking like a mere 
appendage of the gametophyte; but as we ascend, we 
shall see how the gametophyte becomes more and more 
subordinated to the sporophyte, which finally becomes 
an independent long-lived plant, while the gametophyte 
