442 PLANTS AND THEIR RELATION TO MAN 



have leaf green because it lives in a good light. Indian Pipe, 

 or Nun-of-the- Woods, often grows in the ground side by side 

 with arbutus and violets. It never has any leaf green, no 

 matter how good the light, while arbutus and violets always 

 have it. It is known from observation that a plant must 



have both leaf green and light in 

 order to make food for itself from soil 

 water and carbon dioxide. " Beech 

 drops " cannot make their own food 

 even though bright sunlight shines 

 upon them, because this plant always 

 lacks chlorophyll. The whitish waxy 

 Indian Pipes scattered through the 

 dried leaves of the forest cannot 

 make food for themselves because 

 they too lack leaf green. Plants 

 without leaf green send piercing roots 

 into neighboring plants, and steal 

 from them the food manufactured 

 for their own use. Such plants are called parasites. Some- 

 times plants which lack leaf green live upon decaying logs and 

 rotting leaves. They are then called saprophytes. 



The working plant, that is, the plant which takes crude mate- 

 rials from the soil and the air, and makes them into foods, needs 

 light and leaf green for its task. 



The leaves of the plant make food for the plant. Most 

 of the work of food making is done by the leaves since they have 

 the pores through which carbon dioxide enters, since they con- 

 tain leaf green, and since they receive the best light. If a plant 

 loses a large part of its leaves, the supply of food which it is able 

 to make is so meager that the plant starves to death. The 

 caterpillars, which appear in spring and summer and greedily 

 devour the leaves of trees and bushes, rob our plants of their 



FIG. 308. If a strip of black 

 paper is laid across a leaf, it 

 excludes sunlight and turns 

 the shaded part yellow. 



