110 A TEXT-BOOK OF BOTANY 
formed a single large gamete, which remains in the cell that 
produces it. This large gamete, which remains passive, is 
the female gamete or egg, and the globular cell that produces 
it is the odgonitum (egg-case). In the figure (Fig. 99, A 
and B) these large eggs are seen packed with roundish 
masses of reserve food. 
Other cells, either in the same filament or in some other 
filament, differ from the ordinary cells in being much 
shorter (Fig. 99, 4, b, and B, a). In each of them one or 
two gametes are formed and are set free, swimming about 
like small swimming spores (Fig. 99, B, b). These active 
gametes are the male gametes or sperms, and the short cell 
that produces them is the antheridium. 
The sperms swim actively about in the vicinity of an 
odgonium, and sooner or later one enters through an open- 
ing in the odgonium wall and fuses with the egg (Fig. 99, 
B,c). Asa result of this act of fertilization an odspore 
is formed that soon organizes a firm wall about itself (Fig. 
99, A,c). This firm wall indicates that the odspore is not 
to germinate immediately, but is to be protected through an 
unfavorable season, such as failure of food supply, cold, 
or drought. 
It is evident, therefore, that although both the swimming 
spores and the odspores are able to produce new plants, the 
former germinate immediately and enable the plant to 
spread during the growing season, while the latter last 
through the winter when the parent plants have perished, 
and form new plants in the new growing season. 
The most important fact illustrated by Gdogonium is 
that the gametes are not alike, as in Ulothriz and Clad- 
ophora, but have become very unlike. One of them (the 
egg) is relatively large and passive; the other (the sperm) 
is relatively small and active. In this case, therefore, the 
two sexes are apparent, and we recognize male and female 
gametes. 
