252 



STRUCTURE AND LIFE HISTORIES 



OUTLINE OF LIFE HISTORY OF ULOTHRIX 



Plant Body 

 (Undifferetitiated into gametophyte and sporophyte stages) 



1 



Physiological 

 Sporangium 



I 



Zoospore 



I 



Plant body 



(Undifferentiated into 

 gametophyte and sporo- 

 phyte stages) 



Physiological 

 Gametangium 



I I 



Isogamete Isogamete 



Conjugation 



Zygote 



4, I 



Plant body 

 (Undifferentiated into 

 gametophyte and sporo- 

 phyte stages) 



PLEUROCOCCUS 



242. Habitat. — Everyone is familiar with the green 

 layer found on the outer surface of the bark of trees, on 



Fig. 1 83. — Individual plants of green slime (Pleurococcus vulgar h) , show- 

 ing the tendency of the cells to remain attached after cell-divisions, thus 

 causing transitions from a one-celled to a multi-cellular plant. 



wooden fences, and the moist shaded surfaces of stone 

 steps or rocks. Careful observation will show that this 

 color is largely due to the presence of countless numbers 



