CHAP. CIV. 



7?ETULA CE^.. BE'TVLA. 



169; 



15,50 







Description. The 

 common birch, when 

 of a tree-like size, is 

 known, at first sight, 

 by the silver} white- 

 ness of its outer bark, 

 the smalhiess of its 

 leaves in comparison 

 with those of other 

 timber trees, and the 

 lightness ami airiness 

 of its whole appear- 

 ance. The tree, as 

 comparedwith others, 

 is of the middle size, 

 seldom exceeding 50 

 feet in height, with 

 a trunk of from 1 ft. 

 to 18 in. in diameter, 

 even in the most fa- 

 vourable situations. 

 When drawn up in 

 woods, liowever, in 

 good soil, it has been 

 known to attain the 

 height of from 60 ft. 

 to 80 ft., but never, 

 in such situations, 

 with a trunk of pro- 

 portionate diameter. 

 In the woods of Rus- 

 sia, Pallas observes, 



the birch is tall and erect, with a trunk not very thick ; in the groves, the 

 trunk is thicker, and the head more spreading; and, in the open fields, the 

 trunk is short, the head broader than it is high, and the branches tor- 

 tuous. The trunk is, in general, straight and cylindrical, without deformities 

 and knots. The cuticle is white and scaly in trees from ten to thirteen 

 years of age ; but in old trees the trunk is covered with deep black clefts 

 in its bark. The branches proceed chiefly from the summit, and are alter- 

 nate, frequently subdivided, very pliant and flexible, and covered with a 

 reddish brown or russet-coloured smooth bark, which, as well as the buds, 

 is slightly impregnated with a resinous substance. Both the trunk and 

 branches are occasionally subject to the production of excrescences; the 

 former as large knots, and the latter as twiggy tufts resembling large birds' 

 nests. These twiggy tufts are seldom found on the weeping variety, and 

 abound most on trees of the common sort growing on boggy soil. They 

 are most probably formed by the extravasation of the sap, occasioned by the 

 puncture of some insect. The leaves are alternate, bright green, smooth, 

 shining beneath, with the veins crossing like the meshes of a net ; and the 

 petioles are i in. or more in length. The male catkins appear in autumn, 

 on the ends of the twigs, but do not expand their flowers till the female cat- 

 kins appear in spring. On young trees, and on old trees in particular situ- 

 ations, especially in damp boggy soil, the branches are erect ; but in old trees, 

 and in some young ones more than in others, they are pendulous, and hence 

 the variety of that name. The roots extend themselves horizontally, and 

 divide into a great number of rootlets and hair-like fibres at their extremities ; 

 but they never throw up suckers. The rate of growth is considerable when 

 the tree is young; averaging from 18 in. to 2ft. a year for the first 10 years; 

 and young trees cut down to the ground often make shoots 8 ft. or 10ft. long 



