CHAPTER XLIII 



EVOLUTION AS SHOWN BY PLANTS 



The first plants lived in water, and their whole structure 

 was fitted to this environment. The body consisted of a 

 single cell, and since it was a green cell the plant could 

 make its own food, as we have seen. Some of these very 

 simple plant bodies bore threadlike extensions of their 

 protoplasm called cilia, and plants possessing these could 

 swim actively. Most of these plants, however, had no such 

 power. Their method of reproduction was very simple, 

 the single cell simply splitting and thus giving rise to two 

 new individuals. This method is called vegetative multi- 

 plication, because no special reproductive cell is devoted 

 to the work of reproduction, but it is done by an ordinary 

 working (vegetative) cell. Such simple plants as these 

 primitive ones exist in great abundance to-day. They 

 belong to the great group called Algce, and they may be 

 properly regarded as the forms that "started" the plant 

 kingdom. 



Later in the evolution of plants, cells which clung to- 

 gether began to work together, and a body of several and 

 finally many cells was developed, the commonest form 

 among algae being a simple or branching filament. There 

 were also flat, platelike bodies. 



In the many-celled plant bodies thus formed, special 

 reproductive cells soon appeared. Under certain con- 



339 



