PLANTS IN THEIR RELATION TO HUMAN WELFARE 127 



on oxidation in order to live and grow, and must reproduce 

 their kind in order to perpetuate the species. We turn now 

 to a discussion of some of the uses of plants to man, and some 

 of the ways in which they are injurious. 



I. SOME OF THE USES OF PLANTS TO MAN 



135. Uses of plants for food. By repeated experiments 

 we have proved that various parts of plants contain generous 

 stores of starch, 

 sugar, protein, 

 and mineral mat- 

 ters. In our study 

 of human biology 

 we shall find that 

 the foods which 

 are essential for 

 our bodies are 

 composed of these 

 same substances. 

 It is for this 

 reason that man 

 and other animals 

 are so largely 

 dependent upon 

 plants for food. 

 As examples we 

 may mention 

 roots like pars- 



FIG. 61. Coffee tree. Notice coffee berries along 

 sides of branches. (Courtesy of New York 

 Botanical Garden.) 



nips, beets, 



and sweet pota- 



toes; stems, like 



common potatoes, asparagus, and sugar cane ; leaves, such 



as cabbage and lettuce; flowers, for example, cauliflower; 



