EVOLUTION AS SHOWN BY PLANTS 341 



egg is called the fertilized egg, and this process is the same 

 in plants and animals. 



All this progress in evolution was made by the Algae 

 and it may be summed up as resulting in plants with many- 

 celled bodies reproducing by vegetative multiplication, by 

 swimming spores, and by fertilized eggs. 



The next great advance was the emergence of plants 

 from the water to the land, and this important step seems 

 to have been responsible for all the later development of 

 the plant kingdom. In other words, had plants always 

 remained in the water, there is very good evidence for the 

 belief that they would never have developed into forms 

 much more complex than the ones which have been de- 

 scribed. Land plants are more complex and diversified 

 than water plants, just as land conditions are more varied 

 than aquatic conditions. Thus always, to some extent, we 

 find a reflection of the conditions of the environment in the 

 structures of the organisms which inhabit that environ- 

 ment. 



This emergence from the water and the formation of the 

 land habit were accomplished by that great group of plants, 

 next above the Algae, which comprises the liverworts and 

 the mosses. The land habit means exposure to air instead 

 of to water, and the danger to be guarded against is the 

 drying out of the body. We recognize that water is the 

 primary need of the animal as well as the plant body, and 

 that the individual cells of our body require a fluid medium 

 for their life just as truly as a fish requires water. This 

 fact alone is strongly suggestive of the remote aquatic 

 ancestry of all living things. Plant bodies became more 

 compact, but for a long time could live on land only by 



