OF THE 6TBUCTURE OF WOOD AND HEBBS. 83 > 



SECTIONS OF WOOD. 



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 the 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 numerous 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 I) 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 intervals. The wood extends through- 

 out the space D C 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 year is comprised within the space K L M N ; while that 

 of the third year is represented by the space M N E F. The size of the pith, E F 

 G, is small compared with that of the wood; but its cells are much larger than 

 those belonging to the pith of the Holly. The small figure at the bottom of the 

 plate represents the large section of its natural size. 



^ENGLISH OAK. A section of Oak varies in some respects from the several kinds 

 of woods which have already been described. The vessels of the bark are arranged 

 in different ways. Through the middle of the bark extends an unbroken arched 

 band of vessels, while a row of large oval clusters, standing at equal distances from 

 each other, intervene between it and the wood. The vessels of this inner row are 

 of a peculiar nature, and are termed by Grew rexiniferous vessels, since they contain 



