loS 



(b) Anatomy. 



The tracheids of the xylem have a smaller diameter than those of its con- 

 geners and also thinner walls, consequently tangential and radial sections look 

 much more delicate objects under the microscope than in the other species. 



The medullar\- rays resemble the prosenchymatous cells in their structure, 

 although, of course, not in form ; these parenchymatous cells are very long and 

 narrow, and are fairly distinctive characters of the species, as also are the numerous 

 simple cells with their oblique slits or perforations. 



The dark cell substance is only sparsely distributed in the tracheids, but 

 pronounced in the medullary rays. The bordered pits are both numerous and 

 of comparatively large diameter in proportion to the narrow lumina. 



Figure 54 shows a trans\'erse section through the timber tracheids, the 

 autumnal growth being indicated by the smaller lumina near the top of the picture, 

 the tracheids having the dark-coloured contents are few in number and scattered 

 irregularly through the centre of the picture. The medullary rays run from top to 

 the bottom of the plate, and all have the manganese compound contents. Figure 55 

 gives a higher magnification of a similar section to Figure 54, the autumnal wood 

 running across the centre of the picture, but showing less brown contents in the 

 cells. Figure 56 illustrates a radial section more particularly showing two 

 medullary rays — the parenchymatous cells more or less containing manganese 

 compound. No marginal tracheids are present in the rays, and the simple cells 

 of these bodies are clearly seen. The autumnal growth is to the right. This 

 plate also conveys an idea of density over that of its congeners. Figure 57 is a 

 longitudinal tangential section. 



V. BARK. 



(a) Economic. 



Owing to the limited amount of tannin in its cells it cannot claim to be a 

 tannin bark of any pretensions. 



(b) Anatomy. 



There are one or two points of differentiation in this bark from its 

 congeners, for instance, it contains less tannin cells than any other species, and 

 there are also fewer strands of cork or periderm cells. Here the bast cells do not 

 preserve in cross section so constant a shape as in other species, where the usual 

 form is consistently rectangular with the long axis tangential, whilst in this 

 species that character obtains near the camhimn, yet a gradual shortening outwards 

 of this axis occurs until the long axis is parallel to (lie medullary rays or radial, 

 and a ring of these can be seen in Figure 58, at the top, although not (piite focussed. 



