32 



BOTANY 



PART I 



of the shoot have been distinguished as SCALE leaves, foliage 

 LEAVES, bracteal LEAVES, and FLORAL LEAVES (Fig. 34). These 

 usually succeed one another in definite order. However unlike the 

 leaves may become, their first origin is similar. Since the scale leaves 



Fig. 33. — Arer pJc.taywides. A, external view of a bud, with two young leaves between 

 wliicli tlie apical cone of the stem is visible ; sp, the leaf-blade, in which live 

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

 the growth of which the leaf-stalk will arise later. E, an older leaf seen from the 

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

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

 diagramniatically. D, a transverse section of the basal portion of a bud showing 

 three vascular bundles in each leaf. K, a similar section at a higher level ; the 

 number of vascular bundles has increased by branching. (After Deinega, from 

 Goebel's Organography. A, B, and E, slightly magnified.) 



and bracts can often be shown to be arrested forms of foliage leaves, 

 the latter may be first considered. 



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

 structure.s on which devolve the task of providing nourishment 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 simple, as in the needles 

 of Conifers, the primordial leaf simply increases in length without any 

 farther difrcrentiution into parts. In other undivided leaves, however. 



