278 



ALG.'E 



zoospores, as also thaii those which si)ring from the zygosperms resulting 

 from the conjugation of the zoogametes. The escape of the swarm-spores 

 was observed by Cramer to take place, usually in the morning, even in 

 water which froze on the surfoce every night, conjugation following 

 quicklv afterwards. The two kinds of swarm -spore are never produced 

 in the same cell, but in different cells of the same filament, and Cramer 

 believes that conjugation takes place between zoogametes from the same 

 filament. The megazoospores use up in their formation the whole proto- 

 plasmic contents of the mother-cell, while in the production of the 



Fig. 24,6. — Ulothri.x hnplexa Ktz. a, vegetative filament (x 4S0) ; b, portion of the 

 same (x 800) ; c, palmella-condition ( x 480) ; d, esjape and conjugation of zoogametes 

 (x 8od). (After Dodel -Port.) 



microzoospores or zoogametes a portion of the contents forms a bladder 

 which escapes with them, but soon perishes. According to Wille (Bot. 

 Centralblatt, vol. xi., 1882, p. 113) Ulothrix also produces cysts or rest- 

 ing-spores, which may be either aplanospores or akinetes. In some 

 other members of the order the filament is branched. Schaarschmidt 

 points out that a state closely resembling the microsporiferous filaments 

 of Ulothrix occurs in the development of the Confervaceae ; and 



