58 INTRODUCTION TO BOTANY 



of cork which form outside the green bark. Photosynthetic 

 work is also done by the stems of most common annual plants 

 of the farm and garden, such as corn, beans, peas, and potatoes. 



FIG. 39. Twigs of coffee tree, showing how leaves are supported so as to 

 give them complete exposure to light 



57. The stem raises leaves into the light. Competition for 



light is extremely common among plants. One of the main 

 reasons why the surface of the earth in a very dense forest 

 the forest floor, as it is called is comparatively bare of 

 flowering plants is that they cannot get enough light there 

 to live. In a cornfield it often seems as if the weeds were 



