32 



BOTANY 



Foliage Leaves, generally referred to simply as leaves, are the 

 leaf structures on which devolves the task of providing nourish- 

 ment for the plant. Since the exercise of this function is dependent 

 upon the presence of the green pigment, foliage leaves have a 

 green colour. In certain cases, where their form is extremely 



FIG. 33. Acer platanoides. A, external view of a bud, with two young leaves between 

 which the apical cone of the stem is visible ; sp, the leaf-blade, in which five 

 segments are indicated, the uppermost one being developed first ; st, the zone, by 

 the growth of which the leaf-stalk will arise later, li, an older leaf seen from tin- 

 side ; the young vascular bundles, which will later determine the venation, are 

 indicated. C, fully-grown leaf, with the course of the vascular bundles in- 

 dicated diagrammatically. D, a transverse section of the basal portion of a bud 

 showing three vascular bundles in each leaf. ./,', a similar section at a higher level ; 

 the number of vascular bundles has increased by branching. (After 1 (KIXKOA. from 

 GOEBEL'S Organography. A, li, and K slightly magnified.) 



simple, as in the needles of Conifers, the primordial leaf simply 

 increases in length without any further differentiation into parts. In 

 other undivided leaves, however, whether lanceolate, elliptical, ovate, 

 or otherwise shaped, the flat leaf-blade is distinct from the leaf-base, 

 while a leaf-stalk may also be interpolated between them. If no 

 leaf-stalk is developed the leaf is said to be SESSILE, otherwise it is 

 described as STALKED. 



