THE GREAT GROUPS OF ALGiE 



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 

 Algas, 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, (Gonatone- 

 ma), showing formation of 

 zygote without conjugation. 

 — After WlTTEOCK. 



