28 BOTANY. 



plants already mentioned, small motile cells, called spermatozoids, are 

 formed. These are much smaller than the egg cell, and resemble the 

 zoospores in form, but are much smaller, and without chlorophyll. When 

 ripe they are discharged from the cells in which they were formed, and 

 enter the oogonium. By careful observation the student may possibly be 

 able to follow the spermatozoid into the oogonium, where it enters the egg 

 cell at the clear spot on its surface. As a result of the entrance of the 

 spermatozoid (fertilization), the egg cell becomes surrounded by a thick 

 brown wall, and becomes a resting spore. The spore loses its green color, 

 and the wall becomes dark colored and differentiated into several layers, 

 the outer one often provided with spines (Fig. 16, F). As these spores do 

 not germinate for a long time, the process is only known in a compara- 

 tively small number of species, and can hardly be followed by the ordi- 

 nary student. 



Much like (Edogonium, but differing in being branched, is 

 the genus Bulbochcete, characterized also by hairs swollen at 

 the base, and prolonged into a delicate filament (Fig. 16, G). 



The highest members of the Confervacece are those of the 



FIG. 17. A, plant of Coleochsete, x 50. B, a few cells from 

 the margin, with one of the hairs. 



genus Coleochcele (Fig. 17), of which there are several species 

 found in the United States. These show some striking resem- 

 blances to the red seaweeds, and possibly form a transition 

 from the green algae to the red. The commonest species form 



