252 



STRUCTURE AND LIFE HISTORIES 



OUTLINE OF LIFE HISTORY OF ULOTHRIX 



Plant Body 

 (Undifferentiated into gametophyte and sporophyte stages) 



Physiological 

 Gametangium 



4 'i- } Reduction 



Isogamete Isogamete 



Conjugation 



Physiological 

 Sporangium 



Zoospore 



4 4 



Plant Body 



(Undifferentiated into 

 gametophyte and sporo- 

 phyte stages) 



Zygote 

 Swarm-spores 



4 4 



Plant Body 



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 vulgaris) , 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 

 crool is largely due to the presence of countless numbers 



