VEGETABLE PHYSIOLOGY. 25 



Of the Branches. 



Branches are the subdivisions of a stem or trunk, which are 

 found on many herbaceous plants, but are chiefly noticed on 

 shrubs and trees. The primary branches spring immediately 

 from the trunk ; the secondary ones from the primary ; and so 

 on in a regular subordination, till they terminate in slender twigs. 

 They consist of precisely the same anatomical parts as the trunk, 

 and with the exception of a root, are in fact little trees, which, if 

 separated from their parent stock, and planted in the earth under 

 favorable circumstances, would throw out roots, and become 

 independent plants. They proceed from buds formed within 

 the surface of the trunk, which interrupt the parallelism of its 

 fibres, and form knots in the wood. These knots afford a point 

 of support and centre of motion to the growing branches, and 

 are sunk more deeply in the wood in proportion to their age. 

 Branches are supposed to originate from a convolution of vessels ; 

 so long as the vascular bundles proceed in an uninterrupted 

 straight line, so long will the stem remain straight ; but whenever 

 they form a knot, nature appears to make new efforts, and a 

 branch is produced. 



The lower branches are often nearly parallel to the horizon at 



right angles with the trunk : those above them make angles more 



and more acute, as they are placed nearer the summit ; but 



these angles differ in different species, and in every individual 



tree are subject to numerous varieties, from the influence of 



external causes. Some branches produce only leaf and new 



branch buds : others produce only flower buds. The former 



are smooth in their surface, pliable and tough, with close straight 



fibres, easily separated from each other : the latter are wrinkled 



at their base, have their fibres less compact, and break short 



when struck. There are also branches which pierce the bark 



without a bud, and form what is commonly called false wood. 



These, as they are often luxuriant in their growth, and rob the 



more useful branches of their due nourishment, are carefully 



1 4 



