88 VIEWS OF THE MICROSCOPIC WORLD. 



ELM. The section of an Elm branch which appears in drawing 132, is an ex- 

 ceeding rich figure, and the several divisions are boldly defined. The skin of 

 the bark A B possesses considerable thickness, and the pores of the cellular 

 tissue belonging to this integument, are exceedingly small. 



Throughout the bark bundles of the proper vessels are seen profusely scattered 

 in oval or egg-shaped clusters, and beyond it the sap-wood, comprising the 

 space DOTS. The whole of the true wood is included in the space D C E F, 

 and is the growth of four years and a half. The annual rings are very distinctly 

 marked ; the first extending from E to Q, the second from Q to O, the third 

 from to M, and the fourth from M to K ; while the remaining half year's 

 growth occupies the space K L D C. The vessels dispersed through the wood 

 differ very much in size ; the larger, disposed in circular bands, are arranged on 

 the inner margin of every annual ring, occupying the positions Q R, P, and M N, 

 K L ; while others are scattered promiscuously throughout the wood, and are 

 more numerous near the centre of the section than in the more recently formed 

 wood towards the margin. The more minute vessels are seen stretching in deli- 

 cate and broken chains across the rays of cellular tissue, emanating from the 

 centre ; the various positions of the rays being indicated by the white lines in 

 the figure running from the pith E G F, and penetrating for some distance into 

 the bark. The rays of cellular tissue possess great uniformity in their respect- 

 ive thicknesses, as well as in the intervals by which they are separated from one 

 another. The rays are usually arranged at equal distances from each other. 



ENGLISH WALNUT. In drawing 133 is displayed a magnified section of a branch 

 of English Walnut, four years old, and which presents a most beautiful configura- 

 tion. A B indicates the position of the skin of the bark, and the latter envelope, 

 with its cellular tissue, and proper vessels, is comprised within the space A B C D. 

 The proper vessels collected together in round clusters are distributed in two 

 circular rows H I and R S, deeply situated within the bark. The wood is in- 

 cluded in the space D C E F. The first annual ring extending from E to O, the 

 second from O to M, the third from M to K, and the fourth, including the ring of 

 sap-wood, P D, from K to D. The sap-vessels distributed through the wood 

 are not numerous, but their size is comparatively great, and, as in the Elm, they 

 are grouped more thickly together near the pith, the cells of which are quite 

 large compared with those of the pith of the Elrf . The pith itself is also much 

 larger than in many other woods of the same age. The radial lines of 

 cellular tissue in the Walnut observe no uniformity in respect to their relative 

 thickness, as is the case of the Elm, neither are they arranged at equal distances 

 from each other. 



But the most remarkable peculiarity in the Walnut is the broad white arched 

 bands, running across the rays of cellular tissue, four of which are exhibited in 

 the figure before us ; in the Elm they are also seen disposed in a similar manner 

 but much narrower. Their existence is attributed to the same circumstances 

 that cause a similar appearance in the Oak ; namely, the greater compression of 

 the cellular tissue where these bands occur than in other portions of the wood. 



