OF THE STRUCTURE OF WOOD AND HERBS. 80 



twig are here distinctly seen. C F G is the pith, consisting of cellular 

 tissue, and the cells are evidently much larger than those in other parts of the 

 section. The wood is comprised within the space H I C F, and the numer- 

 ous spiral and sap- vessels which traverse it are represented in position by the 

 circular dots with which this space is filled. Running from C F to D D are a 

 great number of lines, some broad and others narrow, which divide the vessels 

 from each other ; these insertions are the cellular tissue of the wood, and are 

 regularly arranged around the pith. Two of the larger insertions are shown in the 

 figure. The first annual ring of wood occupies the space C F M N, the second, 

 M N K L, and the third K L H I. The bark extends in thickness from A to 

 H, and consists of the skin A B, portion of a ring of cellular tissue P P, and a 

 row of proper vessels H I, situated in the inner margin of the bark. The space 

 D D H I represents the sap-wood, which is also traversed by minute insertions 

 of cellular tissue radiating from the pith. 



PEAR TREE. In drawing 128 is presented one-eighth part of a section of a 

 branch of a Pear tree, both magnified and of its natural size. It exhibits, of 

 course, the same general features as the section of the Holly, but varies in some 

 particulars. The rows of vessels stretching out from the pith to the bark, are 

 less broken than in the Holly, and the rays of cellular tissue are more regularly 

 arranged ; branching out at equal distances from each other, and presenting, with 

 the numerous vessels dispersed throughout the wood, a remarkably elegant figure. 

 The three rings of the true wood E F M N, M N K L, and K L D C, denoting 

 the age of the branch, are distinctly marked ; and beyond them the sap-wood 

 occupies the space D C H I. The bark is comprised within the space H I A B, 

 and is formed of the minute cells of the cellular tissue, interspersed with numer- 

 ous figures of an oval shape. These last are clusters of proper vessels of the bark, 

 and are rounder in form, and more numerous, the nearer they approach the wood. 



THE HAZEL. A section of a Hazel branch, when magnified, exhibits a figure 

 of exquisite beauty and symmetry. In drawing 129, an eighth part of an entire 

 cross section of a bough three years old is faithfully delineated. The bark, which 

 is included within the space A B C D, is enriched with clusters of vessels of 

 various shapes and figures. The skin of the bark is represented by the ring A 

 B, to which succeeds a broad band Q Q, consisting of the cells of the cellular 

 tissue ; within this band is another ring H I, composed of sap-vessels. The 

 space H I D C, is filled partly with cellular tissue and partly with sap-vessels, in 

 pear-shaped and semi-oval clusters, alternating with each other at equal inter- 

 vals. The wood extends throughout the space D E F, and is divided into 

 regular and equal compartments by great radial insertions of cellular tissue; and 

 these compartments are still further subdivided by more delicate and minute rays 

 of tissue running from the pith to the bark. Throughout the wood spiral 

 vessels are profusely scattered, and are found to be most numerous near the 

 bark, or in the growth of the last year, D C K L. The growth of the second 



