THE BARK 



151 



separability from one another, that is, into 

 laminae, together with the surface char- 

 acters of the latter, the external color and 

 level markings, the presence and nature of 

 parasites, and the color and inequalities of 

 the inner surface. 



The Laminae. — The laminae do not 

 depend entirely upon diiferent tissue com- 

 position. The same tissue, produced at 

 different times, may present differences 

 sufficient to result in different degrees of 

 cohesion, as well as markedly different 

 color, at different depths, so that separation 

 may readily occur, or they may readily be 

 distinguished in sections. 



Section-markings. — Groups or radial or 

 tangential rows of tissue-elements, differing 

 from those adjoining, frequently produce 

 gross markings on the section-surface. 



Fracture. — The fracture of barks or of 

 their individual layers is denominated in 

 general as being brittle or tough. Various 

 modifications are soft, earthy, granular, 

 horny, waxy, fibrous, splintery, or flexible. 

 A bark may be flexible in one direction and 

 not in another. 



The Outer Surface. — The outer surface is 

 described in general as being harsh, rough, 

 downy, smooth or shiny, and its luster may 

 be waxy, vitreous, and so on. Some of the 



f\. i 



Fig. 425. Section of young CaJisaya bark, showing wrinkling 

 in drying. 426. Section of old Succirubra bark, showing 

 ridging. 



rig. 427. Quill of mature Cali- 

 saya bark, showing transverse and 

 longitudinal fissures. 



