CHAPTER XIV. 



NON-TYPICAL LEAVES AND THEIR SUBSIDIARY 

 FUNCTIONS. 



The leaf the most plastic organ of the plant Heterophylly 

 Conversion of leaves to bud-scales Leaves of Conifers 

 Relative transpiratory activity of various trees The Larch 

 Adaptation to environment Floating and aquatic leaves 

 Rolled leaves Leaves of arid situations Adaptations to 

 prolonged drought " Switch plants "Leaf- tendrils and leaf- 

 spines Phyllodes and Phylloclades. 



THE student is now acquainted with the principal types 

 of leaves and their chief functions. It remains to enquire 

 more closely into cases where modifications or alterations 

 of form and structure, and even of function, disguise the 

 characters of the leaf; and we shall find that these have 

 gone so far in some instances, that no one would suspect 

 at first sight that the given organ is a leaf at all. 



It will be remembered that we found plenty of ex- 

 amples in the leaves of the Leguminosa? of special 

 adaptations to peculiar purposes. Who would suppose 

 that the tendril of Lathyrus Aphaca, for instance, is a 

 leaf, unless he had compared the transitional cases ? 



So numerous and important are the modifications in 

 leaves, that it is hardly too much to say that the student 

 who is well versed in them and their interpretation has 



