PLANT LIFE AND OURS 39 



which gives a real basis for that feeling of kinship to 

 nature to which we have referred. 



Our life depends absolutely upon certain things. Chief 

 among these things are food and air and water. With- 

 out them we die. Plant life also depends upon food and 

 air and water. It has the same needs for them that we 

 have. Our whole body is mainly an equipment for secur- 

 ing these things and using them. Our bodies are chiefly 

 composed of bone and muscle, of blood and the digestive 

 organs, and the principal work of all these parts is to secure 

 food and use it. Similarly a plant is composed principally 

 of roots, stems, and leaves, and the principal work of 

 these parts is to secure food and use it. 



Plants are much like ourselves, then, in their relations to 

 food and air and water; here are three life relationships 

 necessary to living things whether they be plants or ani- 

 mals. But there is another life relationship of plants in 

 which they are different from animals. That is the rela- 

 tionship to light. Animals can live in the dark, but green 

 plants cannot. They must have light, and it is their need 

 for light which explains the form of their stems and leaves 

 more than anything else explains it. Look at Figures 10 

 (page 55), 73 (page 210), 74, 76, and 78. Also consider the 

 forms of green plants wherever you see them. Do they 

 not all appear to be seeking the light? 



To get light, to get food, to get air, to get water, and to 

 reproduce, appear to be the chief ends of plant life ; herein 

 we have the principal secret of plant structures ; herein 

 we have a sort of formula by which we may explain 

 the parts of plants which we study. These are the 

 great purposes, and, in some way or other, each part 

 serves these purposes. You will see many kinds of plant 



