THE BIRCH TREE. 
Betula alba, L. 
Pee Gl KOBE GrAUN lp ey 
Patterdale, Westmorland. 
Tue sylvan bank, the pastoral hollow, the steeply acclivitous 
ledge, and the fell rising into mountain solitude are invested 
by the silvery bark and feathery evolution of foliage of this the 
‘queen of the woods.’ The tree belongs more to lowlands and 
uplands than to mountains, but it serves frequently to charmingly 
hide or relieve the savageness of the mountain wastes, whereto 
it imparts an aspect of picturesqueness and witchery. It shuns 
the dingle and the coomb, imperatively demands light, and is 
highly accommodating as regards power of resistance to great 
extremes of heat and cold. For all these and other reasons, 
this tree intrudes itself very forcibly on the attention of the 
naturalist and the nature-lover ; and a brief description of its 
chief anatomical, chemical, and physiological characteristics 
will therefore, it is hoped, prove acceptable. 
Szem.—The wood is of medium hardness and weight (specific 
gravity 0.5 to 0.76), entirely white, homogeneous, with no dis- 
tinct alburnum, z.e. it is a sap-wood tree, no heart-wood. The 
medullary rays are mostly in one row (three or four rows in old 
wood), are 6 to 8 per millimetre of arc, rather irregularly 
spaced, and about 1 mm. high; the vessels are rather large, 
being about 85 » average width, are isolated or disposed in 
radial rows of two to four through the whole width of the 
annual ring, their lateral walls are very thickly beset with 
minute pores, and their transverse wall is scalariform; the 
fibres are about 12 » broad, have thickish walls beset with a 
few simple pores; the parenchyma is sparse and occurs in very 
straight transverse bands, or else isolated. In the bark, the 
liber parenchyma forms tangential bands of one to four rows 
of cells, which are narrow and high, and have large simple 
punctures on their radial walls ; the sieve-tubes are elongated, 
have wide lumen and thin walls provided with sieve plates ; the 
bast fibres appear as isolated bundles in the first year of growth, 
and later on sclerenchyma is formed between these groups so 
that ultimately a completely closed sclerous ring (peri-cycle) is 
developed; there are no secondary bast-bundles, they being 
replaced by groups of scleroblasts (stone-cells) representing 
highly lignified parenchyma. After the fall of the epidermis 
in the three year old branches, a suberous envelope of flat 
1g07 June rt. 
