116 



LEAVES AND THEIR WORK 



the changed condition of the seedling grown in the dark only by 

 assuming that light has some effect on the protoplasm of the 

 seedling and induces the growth of the green part of the plant. 

 Numerous instances could be given in which plants grown in 



sunlight are healthier and 

 better developed as to 

 their green parts than 

 those in the shady parts of 

 a garden or field. On the 

 other hand, some plants 

 thrive in the shade. Such 

 plants are the mosses and 

 ferns. Still other plants, 

 minute organisms hardly 



The growth of young stems and leaves of oxalis vigible ^ th 4 t 



toward the light. 



thrive in the light, and 



may be killed by its influence. Such are molds, mildews, and 

 some bacteria. Such plants, however, are not green. As a 



Two stages in an experiment to show that green plants grow toward the light. 



matter of fact, the stem of a green plant which has but little 

 chlorophyll develops somewhat more rapidly under conditions 

 where it receives no light. 



