THE GREAT GEOCJPS OF ALG^E 
247 
spore is organized. As the gametes 
look alike, the process is conjuga- 
tion, and the sex spore is a zygote, 
which, with its heavy wall, is rec- 
ognized to be a resting spore. At 
the beginning of each growing 
season, the well-protected zygotes 
which have endured the winter 
germinate directly into new Spi- 
rogyra filaments. 
On account of this peculiar 
style of sexual reproduction, in 
which gametes are not discharged, 
but reach each other through spe- 
cial tubes, Spirogyra and its allies 
are called Conjugate forms that 
is, forms whose bodies are " yoked 
together " during the fusion of the 
gametes. 
In some of the Conjugate forms 
the zygote is formed in the connect- 
ing tube (Fig. 215, A), and some- 
times zygotes are formed without 
conjugation (Fig. 215, B}. Among 
the Conjugate forms the Desmids 
are of great interest and beauty, 
being one-celled, the cells being 
organized into two distinct halves 
(Fig. 216). 
168. Conclusions. The Green 
Algae, as indicated by the illustra- 
tions given above, include simple 
one-celled forms which reproduce 
by fission, but they are chiefly fila- 
mentous forms, simple or branching. These filamentous 
bodies either have the cells separated from one another 
17 
FIG. 215. Two Conjugate forms : 
A (Mougeotia), showing for- 
mation of zygote in conjuga- 
ting tube ; B, C ( Gonatone- 
ma), showing formation of 
zygote without conjugation. 
After WITTROCK. 
