82 THE TISSUES OF PLANTS. 



the stamens exhibit active movements during the period of 

 fecundation, and these movements are evidently made in 

 order to secure the proper application of the pollen to the 

 stigma of the pistil. These parts are probably subject to a 

 similar principle of contractility to that which influences 

 the movements of the leaves of the mimosa. 



The organization of plants corresponds with this simpli- 

 city of their functions. We have already indicated the 

 predominance in animals of nitrogen, which exists only 

 sparingly in plants. Analysis also only shows us two ele- 

 mentary tissues in plants, the cellular and the vascular, 

 whereas we find in animals six, viz : the cellular, the 

 fibrous, the muscular, the nervous, the osseous, and the 

 cartilaginous; the last four being developed especially in 

 connection with their superadded functions of sensation and 

 locomotion. 



We have therefore in the plant, the functions of nutri- 

 tion and reproduction, operating under greatly simplified 

 conditions. It is therefore proper to begin with the plant 

 as introductory to the study of the more complicated con- 

 ditions under which vegetative life exists in the animal. 



