THE ALGLE 221 



complex organs which are always associated in higher plants 

 with the processes of nutrition. The single cell of which the 

 plant body of Protococcus is composed is thus a very general 

 cell as regards its life functions, in comparison to the highly 

 specialized wood, bark, or leaf cells of higher plants. These 

 cells have become differentiated to perform particular kinds of 

 work in a complex organism, like a single worker in a large 

 factory. The Protococcus cell, on the contrary, is more like the 

 general workman, since it is able to perform all of the life func- 

 tions by means of its single highly differentiated protoplast. 



All of the simpler 



, , ^ Cytoplasm 



algse resemble Proto- 

 coccus in this respect ; 

 that is, in being com- 

 posed of cells which 

 are highly organized 

 but independent of FIG. 115. Protococcus 



each Other in the per- , single Protococcus plant ; b, division of the plant 



f ormance of their life into two cells by f u di ion I c ' four cells formed 



by cell division 



functions. 



Reproduction. In Protococcus reproduction takes place solely by 

 the vegetative method. Its reproduction is thus comparable to 

 that of higher plants which reproduce by means of buds, bulbs, 

 and runners. When Protococcus is about to reproduce vegetatively, 

 each cell divides into two daughter cells which are furnished with 

 one half of the original protoplast, plastid, and nucleus. This cell 

 division takes place by mitosis in a manner similar to that 

 already described for root-tip cells. The daughter cells thus 

 formed then divide again, and this process may be repeated 

 many times. The cell colonies thus produced usually remain 

 united for a time, forming the granular incrustations commonly 

 seen on trees and stones inhabited by Protococcus. These minute 

 cell colonies ultimately separate into individual plants, which 

 are light enough to be disseminated by the wind. Water may 

 .also be a factor in the distribution of Protococcus where they are 

 located on soil or rocks. The above facts account for the wide 

 dissemination of Protococcus in nature. 



