124 DEVELOPMENT OF COMPOUND 



The symmetrical bilateral arrangement of the branches 

 therefore disappears as the tree gets olderj and it is still 

 further concealed by the tendency of the concentric growth 

 of the whole tree to repeat itself in the leading branches. 

 This tendency very frequently manifests itself. Cases where 

 two or more similarly-formed stems spring from the same 

 common stock, whose branches are all concentrically disposed, 

 are quite common in the woods. In fact, whenever a Beech- 

 tree {Fagus ferrugined) is old and well- developed, two prin- 

 cipal forms or prototypes may be distinguished within the 

 crown. The one, the form of the tree itself, only less devel- 

 oped, in the concentric growth of the leading branches into 

 which its smooth, silvery-gray yet massive stem divides ; the 

 other, the form of the leaf: for the fibrous portion or skeleton 

 of that organ, only greatly enlarged and developed, has its 

 counterpart in the symmetrical, flattened, spread-out, but less 

 powerful branches of the tree. 



These facts would seem to indicate that the leaf, whose 

 existence and development in relation to the axis is entirely 

 secondary and subordinate, is in reality the prototype accord- 

 ing to which the tree itself is constructed, which type repeats 

 itself in each individual branch — that is to say, each branch 

 represents, prefigures, and copies it. 



The leaf may therefore be regarded as nothing but a pecu- 

 liar modification of the fibre and parenchyma of the branch 

 which it is engaged in constructing ; and the fibre ramifies 

 through its parenchyma as the branch ramifies through the 

 atmosphere — the same general laws being followed in the 

 distribution of the veins and veinlets. 



This truth will be more apparent if we consider the scheme 

 of a system of shoots or of branch ramifications, and the law 

 of their development and association. In the first place, the 

 primary axis of such a system preponderates in length over 

 the first generation of side axes ; and there is also a propor- 

 tionate decrease, not only in the length, of the side axes, but 

 also in the number of vitally-active buds which they produce, 

 and consequently in the extent to which their ramifications 

 are carried. The vegetative power of the branch in fact 



