SPECIAL FORMS OF LEAVES 



271 



FIG. 243. A portion of a Sweet Pea, showing one leaf (Z), a portion 

 of which is transformed into a tendril (t). 



they have lost much or all of their power to make food, and have 

 become apparently useless or have taken on other functions. 



A very common modified form of the 

 leaf is the scale. The most familiar 

 example of scales is furnished by the 

 buds of shrubs and trees, where they 

 form a projection for the inner vital 

 portions of the bud. These scales are 

 considered leaves which have been pre- 

 vented from developing by being so 

 closely crowded in the overlapping ar- 

 rangement. The leaves of underground 

 stems, which do not get to the light, 

 appear as small scale-like bodies with- 

 out green tissue, and apparently have 

 no function. Sometimes scales are 

 fleshy and are used for food storage, as 

 in Lily bulbs, Onions, etc. In the Asparagus the leaves are 

 scale-like and the food-making is mostly done by the stem, 



FIG. 244. A branch of a 

 Barberry, showing the leaves 

 transformed into thorns. 



