252 



STRUCTURE AND LIFE HISTORIES 



OUTLINE OF LIFE HISTORY OF ULOTHRIX 



Plant Body 

 (Undifferentiated into gametophyte and sporophyte stages) 



PLEUROCOCCUS 



242. Habitat. — Everyone is familiar with the green 

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



Fig. 183. — 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 



