ZTGOPHTTA. 



123 



simpler plants is called the asexual mode of reproduction. 

 In the plants under consideration there is barely enough 

 coherence of the cells to enable them to constitute a plant- 

 body, and one can readily see that 

 the same fission of the cells which 

 here increases the size of the plant 

 would, if the cells cohered lesSj sim- 

 ply increase the number of individ- 

 uals. 



260. As might be expected, the 

 filaments occasionally separate 



Fio. 56.-4, beginning of the sexual rnproduotion of a Pond Scum (Spirogyra 

 longata); a, beginning of the formation of lateral tubes; 6, c, the tubes in con- 

 tact. By the protoplasm passing from one cell to the other at a\ &, the mass of 

 protoplasm formed by the union of the protoplasmic contents of the two cells. 

 C two young resting spores (c), each with a cell-wall. They contain numerous 

 oil-drops, and are still enclosed by the walls of the parent-cell. Magnified 550 

 times. 



spontaneously into several parts of a considerable length, 

 and the parts floating away, give rise to new filaments. 

 The separation takes place by the cells first rounding off 

 slightly at the ends, so that their union is weakened at 



