15 



is only about one-sixth of an inch thick, whereas in Sal its thick- 

 ness is from 1 to 2 inches. 



There is usually a considerable difference both in colour and 

 texture between the outer and inner layers of bark, thus in 

 Phyllanthus Emblica the outer bark is pale grey and the inner 

 substance is red ; in most trees and shrubs also the inner sub- 

 stance is distinctly moist while the outer tissue is dead and dry. 



On the stems of young plants and twigs of old trees the 

 exterior of the bark is usually smooth, but on the old stems of 

 trees and shrubs the degree of roughness varies greatly in 

 different species. InSterculia wrens, for example, it is very 

 smooth and affords a marked contrast to the rough bark of say 

 an old Sal tree. Smooth stems may, or may not, be shining : 

 in Anogeissus latifolia the smooth stem is not shining, while 

 in the Birch it is. 



The colour of the external bark is not only different in 

 different species but varies on different parts of one and the 

 same plant. Thus the twigs and branches of Carissa spinarum 

 are bright green, but the old stems are grey, or yellowish. 



The twigs and branches of Berberis aristata are dark red, of 

 Rubus lasiocarpus purple and of Salix daphnoides dark green, 

 or almost black. The colour of the bark on the stems of trees 

 and shrubs is very important for identification and the follow- 

 ing may be noted as examples : 



In Betula utilis it is almost white. 



In Albizzia procera it is greenish. 



In Boswellia serrata it is yellowish. 



In Stephegyne parvifolia it is bluish-grey. 



In Anogeissus latifolia it is pale grey. 



In Terminalia Arjuna it is pale pinkish-grey. 



In Diospyros tomentosa it is almost black. 



In Sterculia urens it is sometimes dark red. 



The texture of the bark also varies greatly in different 

 species : in Betula utilis it is papery, in Erythrina suberosa 

 corky, while in Teak and Cupressus torulosa it is fibrous, i.e. 

 it breaks up into thin long threads. 



The bark of old branches and stems may, or may not, have 

 fissures, or cracks, of various kinds. The stem of Anogeissus 

 latifolia is smooth without characteristic fissures. When there 

 are fissures they may be shallow as in Teak, or deep as in 

 Pinus longifolia. The way in which such fissures run, whether 

 vertically or horizontally, and the way in which they join, or 

 cross, one another are also characteristic. In Buchanania 



