LIGHT AND HEAT 69 



The Fixed Light-Position of Leaves. Every leaf takes 

 up a fixed position with regard to the light, and this 

 position is that in which it receives the maximum average 



FIG. 20. CLIMBING SHOOT OF IVY, SHOWING 

 LEAF-MOSAIC. 



FIG. 21. FLOWERING SHOOT OF IVY WITH LEAVES STANDING OUT ON 

 ALL SIDES OF STEM. 



amount of light. This, of course, is only true of those 

 herbaceous forms of leaves which spread out horizontally 

 to catch as much light as possible. In xerophytes the 



