SECT. IV. THE CORTICAL LAYERS. 325 



SECTION IV. 



The Cortical Layers. 



THE cortical layers, or interior and concentric Their si- 

 layers constituting the mass of the bark, are si^Tnd 

 situated immediately under the cellular integument number - 

 where such integument exists, and where not, im- 

 mediately under the epidermis ; or they are them- 

 selves external. They are distinguishable chiefly 

 in the bark of woody plants, but particularly in 

 that of the Lime-tree, in which they are easily 

 separated by maceration or exposure to the weather, 

 and in which you may readily count a dozen or 

 more in a branch or trunk of any considerable size. 

 They have been thought to correspond in number 

 to the years of the plant's growth : but this opinion 

 is not confirmed by accurate observation. They are 

 more numerous, however, in the trunk than in the 

 branches, which shows that their number is at 

 least in proportion to the age of the plant, if not 

 exactly corresponding to the number of years. 

 They are also thicker in feeble plants than in 

 vigorous and luxuriant plants of the same species, 

 and in the individual plant they are thicker in the 

 root than in the trunk.* 



The outer layers are coarse and loose in their Texture, 

 texture, exhibiting individually a conspicuous and 

 considerably indurated but very irregular net-work, 

 composed of bundles of longitudinal fibres not as- 



* Physique clcs Arbre*, liv. iv. chap. iii. 



