62 THE LEAVES. [CHAP, 



two kinds of leaf one a small, membranous, brown 

 scale-leaf, upon the elongating axes ; the other, a long, 

 green, needle-like leaf, upon the arrested axes. The 

 needle-like leaves are arranged in tufts of 2, 3, or 5 in 

 Pines, or in many-leaved clusters in Larch and Cedar, in 

 consequence of the non-development of the internodes of 

 the excessively short branches which bear them. That these 

 tufts really arise from shortened branches is obvious on 

 examination, for they occupy the axils of the smaller 

 scale-leaves, and some of them occasionally develop their 

 internodes, when, consequently, the needle-like leaves are 

 borne singly upon the shoot, and are separated from each 

 other by more or less marked internodes. In the Oak, 

 the upper nodes of a year's shoot are usually more 

 crowded than lower down. As a consequence, the 

 branches originating in the axils of these upper leaves 

 by way of mutual accommodation, spread apart at a wide 

 angle, hence the characteristic ramification of the tree. 



5 . The cotyledons are the first leaves of the primary 

 stem of the plant. They are usually, but not always, very 

 short-lived, and shrivel up and die at an early stage. In 

 some plants they never leave the testa of the seed, but 

 remain underground, as in the Oak, Chestnut, and Bean. 

 In the Beech, which is nearly allied to the two former, 

 and the Lupine, nearly allied to the last-named, they rise 

 above the surface. 



The first leaves of branches ordinarily differ from those 

 which follow, in being much smaller and often hard and 

 scaly. These are the scale-leaves. They serve as pro- 

 tective organs to the delicate rudiments of the foliage 

 leaves which they enclose. They may be easily found in 

 many of our trees, as Lilac and Horse Chestnut. Both 

 of these are well adapted to show the gradual passage of 

 the scale- leaves into ordinary foliage-leaves, convincingly 

 showing that they are both modifications of one and the 

 same organ. In Beech and Oak the stipules take part in 

 the same protective function. 



Many trees develop each season terminal as well as 

 axillary buds. As before pointed out, it is only by the 

 development of the former that the original stem or its 

 branches are prolonged. Some plants never renew their 

 branches by annual terminal buds, as the Willow and the 



