- 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 



Fio. 20. — Cr^rMBiNO Shoot op Ivy, showing 

 Leaf-Mosaic. 



j^o, 21. ^Flowbeing Shoot or Ivy with Lbavbs standinq out om 



Aix 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 xerophjrtes the 



