CHAPTER V 



THE LEAF. 



I. As previously noted leaves arise in all cases from buds, and 

 are side or lateral appendages of the stems of plants. They may 

 be of many forms but are generally flattened structures, and, with 

 the exception of those known as floral leaves, usually have buds 

 in their axils. Their growth differs from that of the stem and 

 root in being of short duration, for after reaching a certain 

 size their increase ceases. 



2. Foliage-leaf. — ^Those which are most conspicuous upon 

 plants are green and are designated 

 foliage-leaves. They are important organs 

 generally concerned with the manufacture 

 of food needed by the growing part 

 of the plant, and are also organs from 

 which much of the water taken from the 

 soil by the roots is given off into the 

 air. A typical green foliage-leaf (Fig. 29) 

 consists of the following parts — (i) a broad 

 expanded portion termed the blade or 

 lamina ; (ii) a slender stalA or petiole ; and 

 (iii) a somewhat flattened basal sheath 

 which connects the leaf to the stem. 



The leaf-sheath often bears two appen- 

 dages — the stipules — which may be broad 

 and wing-like as in the clovers and pea, or small and narrow 

 as in pear and apple; leaves possessing them are said to be 

 stipulate, while those without are exstipulate. 



68 



IG. 29. — Foliage-leaf of 

 plum. / Lamina or blade ; 

 / petiole ; j stipule. 



