CHAPTER TWO 



PLANTS AS LIVING THINGS 



Thus far plants have been discussed in their relation to men ; 

 they have been considered as objects of interest, and as a part 

 of man's environment that may promote or interfere with his 

 welfare. But, of course, plants do not grow, or flower, or fruit 

 for the sake of animals or man. Their various organs grow and 

 their structures develop as a result of their own life processes. 

 A plant is successful in nature when it secures nourishment for its 

 complete development, and when it produces offspring and thus 

 insures the perpetuation of its kind. 



It is important for the beginner in the study of botany to 

 realize that plants are Hving things. We are accustomed to 

 think of movement as a necessary evidence of life, and to one 

 who has given no thought to the subject a tree may seem more 

 akin to the stones among which it is rooted than to the animals 

 that live about it. But when we study living beings, we find 

 there are activities more fundamental than movement that are 

 regularly associated with all life. As we shall see later, these 

 more fundamental vital processes — such as respiration, growth, 

 and reproduction — take place in plants just as they do in 

 animals, and plants may therefore be considered as truly alive 

 as are animals. 



Parts of a plant. The vegetative body of the ordinary flower- 

 ing plant is made up of three parts : root, stem, and leaves. The 

 root anchors the plant and absorbs water and mineral salts 

 from the soil. The leaf carries on a remarkable process in which 

 water and carbon dioxide are united by the energy of the sunhght 

 to form sugar, thus providing food for the plant. The stem sup- 

 ports the leaves and conducts water and mineral salts from the 

 roots to the leaves, and foods from the leaves to the roots and 

 other organs. The chief advantage of an erect stem is that it 

 can display a large number of leaves to the light. In the roots, 



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