THE GREEN ALCLE 

 B C 



479 



', .,, 



Fig. 310. — Grai)e Dcsmid. Gormination of zygospore -1, protoplast 

 emerging; B, protoplast beginning to divide in half; C, division nearly 

 complete; D, division complete within the thin temporary cell-wall; 

 E, the two dcsmids escaped from the wall; F, one of them dividing by 

 fission; G, the fission nearly complete, ^-\^. (DeBary.) 



!==JI 



Fig. 311. — Pond-scum (Spirogyra sp., Pond-scum Family, Zygneinacew). 

 1, segments of two thread-like plants beginning to conjugate by the 

 protrusion ot adjacent cell-walls toward each other. 2, later stages 

 resulting in the formation of a zygospore (b). Much magnified. (Ker- 

 ner.) — Pond-scums abound on the surface of ponds, forming masses 

 of bright green color through the summer which turn brownish tow^ard 

 spring when conjugation takes place. 



