294 HISTORICAL GEOLOGY 



(4) SEED PLANTS (Spermatophytes). 



This group, distinguished from all except the transi- 

 tional seed ferns by the production of true seeds, con- 

 tains all the higher plants which we ordinarily observe, 

 as well as many which are extinct. It is divided into 

 two important sections: 



(a) Naked-seed section (Gymnosperms) . 



The seeds are naked and there are no flowers, in 

 the common sense of that word. Here belong the 

 pines and other " evergreens," as well as the 

 cycads, palmlike plants now of small impor- 

 tance, but formerly very abundant (Fig. 422). 



(6) Incased-seed section (Angio sperms) . 



Seeds incased in a husk or shell. This section 

 includes the majority of our familiar trees and 

 shrubs, such as oak, elm, apple, palm, rose, etc., 

 and the grasses, grains, and many herbs. To-day 

 it is the most important group of plants, but it was 

 the last to appear, and in the older geologic periods 

 no such types existed. 



Animals. Animals differ so markedly from plants that 

 all but the simplest forms may readily be recognized as being 

 distinct. They have the power of making voluntary move- 

 ments, they have the sense of feeling, and they depend for 

 food on the bodies of plants or other animals. The higher 

 animals also possess the faculties of seeing, hearing, etc., 

 and even of intelligence, characteristics which separate 

 them more and more widely from plants. 



(1) PROTOZOANS. 



The simplest animals are so much like the simplest 

 plants that only a few things, such as the power of 

 motion and evident sensation, distinguish them. 

 Even these tests fail in the lowest forms. Most 



