176 REPRODUCTION OF SPIROGYRA 



walls at the point of contact are absorbed, forming an open pas- 

 sage between the two cells. While this growth has been going on, 

 the contents of the two cells have contracted somewhat and finally 

 the contents of one cell passes through the tube and fuses with the 

 contents of the other cell. Several modifications of the reproduc- 



FlG. 107. Sexual reproduction of Spirogyra: A, in lower portion of figure 

 the formation of the tubes between the opposite cells of the filaments is shown. 

 Above the contents of two cells have united with two cells of another filament, 

 forming two gametospores. B, germination of a gametospore. 



tion process outlined above will occasionally be noted, such as 

 the development of gametospores in either filament or the fusion 

 of the adjacent cells of a filament by means of lateral tubular 

 outgrowth. In other genera, there is a considerable modification 



