184 Keegan: The Chemistry of the Lakeland Trees. 
dermal glands), a bitter yellow colouring matter (alnein); also 
very much mucilage containing tartrates, etc. On the whole it 
will be noticed that the chemical transformations of this highly 
artistic organism are not pushed much beyond the stage of the 
production of colourless. waxes, resins, and balsamic oils, and 
hence the outcome and development of the tannins, phloba- 
phenes, pigments, etc., are considerably restricted, with the 
u result that we have a silvery whitish bark, a non-durable 
timber, and autumn leaves painted golden yellow, and rarely 
crimson or scarlet. 
Alder. Alnus glutinosa. Although. this undoubtedly 
a. interesting species is morphologically and taxonomically closely 
. related to the Birch, yet when chemically investigated we 
immediately discern serious differences in respect to physiology. 
In the Birch, as we have just seen, the deassimilation stops 
short apparently at the resin-forming stage, but in the Alder it 
oxidisable, especially under the influence of alkalies, as is 
plainly palpable.s:hen the bark is cut and the tree felled. The 
wood is also survharged with tannin, and hence its exceptional 
durability (Birch wood is otherwise), its tolerance of water, and 
its usefulness in the manufacture of boats, piles, clogs, etc. 
There is also another pigment (alnein) of a gold yellow tint 
deepened by alkalies, which also aids and abets in the pro- 
duction of the powerful colorific effect ensuing on the exposure 
of the fresh-cut tissues to the air. It is very noteworthy that 
the leaves of this species do not change colour in the autumn, 
i.e., until the stage of final dissolution sets in, the reason being, 
and far too easily and readily forms high red-brown and muddy- 
shaded anhydrides, i.e., the lower anthocyan-forming stage is 
-overleaped. 
Willow. Salix sp. The most distinctive chemical feature 
of these shrubs is, as everybody k oe the presence of the 
remarkable glucoside salicin, Cun which is now much 
employed in medicine .as a tonic and ebrhigs- and in this 
connection it has been noted as a bounteous dispensation of 
nature that those species, e.g., S. pentandra and S. fragilis, which 
no doubt, that the tannin therein is considerable in quantity, 
furnish this drug most abundantly are also those which flourish | 
more peciianan | by stream se loeae late 8 hollows; i.e » localities” 
