OF THE STRUCTURE OF WOOD AND HERBS. 



89 



ASH BRANCH. In drawing 134 is delineated a cross section of part of an Ash 

 branch, three years old, as it appears when magnified to a considerable extent. 

 The skin of the bark is represented in position by the circular line A B. The 

 bark comprises the space A B C D, and is seen to consist of an infinite number of 

 cells formed by the cellular tissue. Within the bark, next to the skin and 

 nearest to the wood, clusters of minute vessels are seen extending in two circu- 

 lar rows from side to side. The pith, composed of large cells, occupies the 

 space I L K, and the wood the remaining portion of the figure. The arrange- 

 ment of the radial insertions of cellular tissue is very beautiful ; the rays 

 diverging from the pith to the bark at equal distances from each other, and 

 maintaining, nearly always, the same size. The position of the large spiral vessels 

 in the wood is very distinctly marked, gathering in arched bands near two divisions 

 of the annual growth. These divisions are seen extending from H to G and from 

 F to E. The small figure in the plate is the natural size of the magnified section. 



MAPLE. A cross section of the firm wood of the Maple is presented in fig- 

 ure 135, highly magnified. The strong dark lines are the rays of cellular tissue, 



Fig. 135. 



emanating from the ce'ntre of the trunk of which this section represents a part. 

 The large oval openings are sections of the spiral vessels which run lengthwise 

 through the trunk, and the rest of the figure shows the true wood filled with 

 minute pores, whose size does not exceed the actual measurement of one twelve 

 hundredth of an inch in diameter. 



DOGWOOD. A magnified cross section of Dogwood is delineated in figure 

 136. This wood is very hard and firm in its texture, and the smaller pores are 

 much more minute than those of the maple and other lighter woods. In the 

 specimen exhibited, a multitude of fine oval pores are seen scattered throughout 

 the wood, the largest of which does not exceed one two-thousandth of an inch 

 in diameter, and the smallest is not more than one three-thousandth of an inch. 



