' CHAPTER II 

 THALLOPHYTES. 1. 



THE PRIMITIVE PLANTS 



8. Definition. Algae are called the primitive plants 

 because they are thought to have preceded the other groups 

 historically. This does not mean that they were neces- 

 sarily the first plants, for plants that have disappeared, or 

 that we have failed to recognize, may have preceded the 

 Algae. But in our present flora, as an assemblage of plants 

 is called, the Algae appear to be the forms that have given 

 rise to the other groups. They are comparatively very 

 simple, but not necessarily very small, for certain seaweeds 

 become as bulky as do the higher plants. 



The Algse are of very little practical importance, hence 

 their study is not due to the fact that men use them. But 

 they are of very great scientific importance, because they 

 illustrate the beginnings of the plant kingdom, and show 

 how the important kinds of plant work are provided for in 

 the simplest way. They are, in fact, a simple introduction 

 to the study of plants. 



9. Water as a medium. If Alga? are the primitive 

 plants, it follows that the plant kingdom began in the water, 

 for Algae grow in water or in very ^ moi_st_places. It seems 

 to be true, also, that the most primitive Algae, as well as 

 those that gave rise to the higher plants, lived in fresh 

 water ; so that the numerous Algae that live along the sea- 

 coasts are not the most primitive, nor have they given rise 

 to higher plants. From this point of view, it follows that 

 the fresh water Algae are the most important to study. 



8 



