XII] KINDS OF BARK 99 



developed. In the majority of cases, however, true bark 

 is developed very early, or even during the first year, 

 especially when, as in Pines, Larch, Ribes, Robinia, Yew, 

 Vine, &c., the first formed periderm lies deep in the 

 cortex. In practice, however, it is not the custom to 

 emphasize these distinctions of the tegumentary system, 

 and foresters are in the habit of speaking of smooth or 

 rough, thin or thick barks, &c., without reference to the 

 mode of origin, a looseness of terminology which leads 

 to difficulties which we shall endeavour to clear up when 

 discussing the subject of branches and the trunks of older 

 trees. 



We are now in a position to understand the principal 

 characters observable on the twigs, branches and stems of 

 various ages of trees and shrubs, and may summarize them 

 under the following heads. 



The colour, smoothness and other characters of the 

 surface of the youngest twigs depend on the properties 

 and persistence of the epidermis; the similar features of 

 one-year-old twigs and the younger branches, on the colour 

 of the periderm, its thickness and abundance, its persist- 

 ence, and its superficial or deeper situation, as well as on 

 the shape, size and abundance of lenticels. 



The peculiarities of older branches and stems depend 

 on the presence or absence of periderm or of bark ; the 

 colour, roughness, hardness, thickness and especially the 

 mode of breaking up or scaling or peeling off of the 

 latter; the formation of ring- bark, scales or tabular areas, 

 crevasses, splitting into fibres, &c., subjects which are 

 dealt with in volume 5 of the present work. 



72 



