CHAPTER III. 

 Leaves. 



LEAVES are the lungs of plants. The food taken in by 

 the roots has to pass through the stem to the leaves to be 

 acted upon by the air, before it becomes sap and is fit to 

 be used for the growth of the plant. No portion of a 

 plant is more varied in parts, forms, surface, and dura- 

 tion than the leaf. 



No one can become familiar with leaves, and appreciate 

 their beauty and variety, who does not study them upon 

 the plants themselves. This chapter therefore will be 

 devoted mainly to the words needed for leaf description, 

 together with their application. 



THE LEAF. In the axil of the whole leaf the bud 

 forms for the growth of a new branch. So by noting the 

 position of the buds, all the parts included in a single leaf 

 can be determined. As a general thing the leaf has but 

 one blade, as in the Chestnut, Apple, Elm, etc.; yet the 

 Horse-chestnut has 7 blades, the Common Locust often has 

 21, and a single leaf of the Honey-locust occasionally has 

 as many as 300. Figs. 17-58 (Chapter VII.) are all illus- 

 trations of single leaves, except Fig. 43, where there are 

 two leaves on a twig. A number of them show the bud 

 by which the fact is determined (Figs. 25, 26, 31, 33, 34, 36, 

 40, etc.); others show branches which grew from the ax- 

 illary buds, many of them fruiting branches (Figs. 37, 42, 

 43, 50, and 54), one (Fig. 51) a thorn}*- branch. 



The cone-bearing plants (Figs. 59-67) have only sim- 

 ple leaves. Each piece, no matter how small and scale- 

 like, may have a branch growing from its axil, and so 

 may form a whole leaf. A study of these figures, together 

 2 " 



