56 P.O. KEEGAN [sULY 
reserve is feeble and readily exhausted. So far they agree, but in the 
Birch the process of de-assimilation is not so complete as that in the 
Alder, In the former it is not pushed much beyond the lavish pro- 
duction of colourless waxes, resins, and volatile oils, and hence the 
outcome of the tannins, phlobaphenes, pigments, etc., is considerably 
restricted. The result is, that in the “queen of the woods” we have 
a silvery whitish bark with about 30 per cent white resin (betulin) 
approaching a wax or camphor in character, and only about 5 per cent 
tannin (all too feeble to impart a crimson coloration to the autumn 
leaves), together with an amount of phlobaphene too small to over- 
power the predominant suberification. The bast of this tree exhibits 
considerable lignification, but it is clear that the phellogen is perhaps 
the most active formative tissue in the entire rind. The case is pretty 
much reversed in the marsh-loving Alder wherein de-assimilation seems 
to reach its highest intensity. The bark of this tree sometimes con- 
tains as much as 20 per cent of a tannin which is highly carbonaceous, 
and very readily forms high red-brown and muddy shaded anhydrides 
of an eminently antiseptic character. The tannin penetrates freely 
into the medullary rays, parenchyma, and pith of the wood (it is very 
sparse in birch wood); in fact, without a doubt the Alder, taken all 
in all, is by far the most richly tannin-bearing of all our forest trees, 
and this constituent is of such a character and composition that it 
subserves the purpose of lenification rather than of embellishment, for 
as a chromogen it is useless save for colours dark and dun. The leaves 
contain a darkish brown oily matter, while the bark of the twigs 
encloses a bright yellow pasty mass of fat, wax, and a trace of volatile 
oil; carotin is very scarce even in the leaves. Cells filled with a 
homogeneous phlobaphenic matter seem mostly to replace or represent 
the highly suberified periderm of its congener the Birch. 
The members of the sub-order Cupuliferae, viz. the Oak, Spanish 
Chestnut, and Beech, are more closely allied in chemical respects 
than the two foregoing species. No member of the vegetable 
kingdom has been more thoroughly and exhaustively investigated 
than the Oak. The peculiar shape of its leaves is no pledge of 
their physiological faculty, which is extremely powerful. The 
amount of starch which this tree produces and stores up (there is 
37 per cent in the acorns) is, I think, considerably greater than that 
of any tree in our woods. A very distinctive variation is, however, 
observable in the Beech, where even in January and February the wood 
is very rich both in oil and starch, every cell of the parenchyma in the 
outer rings being full of the latter (which is not the case in most starch 
trees), and this predominance continues up till April when the wood is 
found still to be rich in oil (in fat-trees generally there is little oil in 
spring or summer). In fact, the Beech, chemically speaking, is a 
peculiarly eccentric organism. Even in its most massively developed 
trunk there is no marked distinction between the heart-wood and the 
