Leaves. 



83 



Fig. 31. 



Mosaic of Virginia Creeper leaves. The 

 plant is climbing a wall and the blades 

 of the leaves stand vertically. 



as little as possible in reaching them, and that in some way 

 the light assists them in manufacturing the starch which is 

 an important food of the 

 plant. Having reached this 

 conclusion, we find it all the 

 more interesting to note 

 how the leaves strive to 

 intercept the light which 

 comes their way, and how 

 the form and size of the 

 ■plant and the disposition 

 and direction of growth 

 of its branches are also 

 adapted to this purpose. 



The same end is attained 

 in various ways by differ- 

 ent plants. When plants are prostrate on the ground or 

 have grown up over a wall, the leaves spread out more 

 or less horizontally in the 

 first instance, but vertically 

 in the last, and intercept 

 nearly all of the light which 

 falls within the radius of 

 the branches (see Fig. 31). 

 When plants are upright, 

 the tiers of branches and 

 leaves are so separated that 

 the light can strike between 

 them; when the leaves are 

 crowded together in ro- 

 settes, the lower leaves 

 grow out beyond the upper ones and produce broad sur- 

 faces only in the exposed area (see Fig. 32) ; or, when the 



Fig. 32. 



Dandelion plant viewed from above. 

 Leaves in rosettes. 



