LEAVES AS STORAGE ORGANS 



53 



leaves when removed from the plant and freely exposed do not be- 

 come entirely dry for weeks. 



Crystals of calcium oxalate and sometimes of calcium carbonate, 

 are often stored in leaves as well as in stems. These are to be re- 

 garded as waste materials. Since a plant has no regular excretory 



h.-' '^i^^^^^^ '^ik-b^'^^^^.y^ 



Fig. 19.— Agave scabra Big Bend, Texas. A plant with succulent leaves. 

 (Photograph by Dr. Omer E. Sperry.) 



organs it is sometimes necessary to store up certain products of 

 metabolism in the form of insoluble crystals in order to get them 

 out of solution. The leaf would seem to be a good place to store 

 such crvstals because when the leaf falls the crvstals are gotten rid of. 

 Crystals stored in the cortex or bark of a perennial stem are also 

 disposed of eventually as the bark sloughs off from the outside. 



