130 



the trunk from which they issue ; but in point of insertion, 

 distribution, and direction, they exhibit considerable variety, 

 furnishing a ground of distinction, occasionally assumed by 

 botanists, in the discriminating and characterizing of species, 

 Like the stem and root, branches increase in width, by. the 

 accession of new layers, and in length, by the addition of 

 new shoots ; but they are not formed merely by means of 

 an horizontal extension of the longitudinal tubes of the 

 stem, but each branch is, as it were, a distinct individual. 

 Hence, the stem is to the branch what the soil is to the plant, 

 the source of nourishment and stability.* 



Branches may properly be considered as among the most 

 important parts of trees, as they certainly are the most beau- 

 tiful. One of the most obvious offices they have to perform, 

 is to support the leaves ; and the leaves, by a respiration per- 

 ceptible and imperceptible, and by the action of the atmos- 

 phere, as above noticed, elaborate the sap sent up by the 

 roots, and convert it into juice fitted for nutrition. The as- 

 cent of the sap from the roots seems to be considerably assis- 

 ted, by a proper number of side-branches, distributed along 

 the stem ; and the general health and vigour of the tree are 

 in the same way increased ; so that it will ultimately attain 

 a greater size, than if deprived of such branches, or very 

 sparingly supplied with them. During the descent of the 

 proper juice, on the other hand, as has been seen, each branch 

 is nourished by the sap prepared by itself; and the surplus 

 quantity beyond what is so employed, goes to the increase, 

 first of the stem, and, in the end, of the roots. From the 

 experiments made by the most accurate observers, we further 

 find, that the solid texture of the wood depends on the quan- 

 tity of the descending sap, and in a great measure likewise, 

 on the slowness of its descent ; both of which objects are 



* Grew, Anat. of Plants, p. 28.— Du Hamel, T. I. p. 93.— Keith, 

 Vol. I. p. 18— 51.— Vol. II. pp. 255, 256. 



