286 ECONOMICAL APPLICATIONS OF BRITISH LICHENS. 
allied tribe of plants. Those habits and appearances which are 
evident to the eye, but which language cannot readily describe, 
are the best means of identification. By observing their habits 
and different phases during the whole year, I can recognize many 
distinct species. About twenty of them I have raised from seed 
(each truly follows the parent plant), and some more I have got 
in embryo. Botanists have invested, but have not yet had cou- 
rage to storm, the thorny fortress ; therefore its treasures are still 
unrevealed behind the chevaux-de-frise.. 
(To be continued.) 
Economical Applications of British Lichens. By W. Laupsr 
Linpsay, M.D., Perth. 
From very early ages and in many parts of the world Lichens 
have been used to a considerable extent :— 
I. In several of the arts; e.g. dyeing, calico printing, weaving, 
paper, parchment, and pasteboard making, perfumery, brewing, 
and tanning. 
IT. As food alike to man and the lower animals in Arctic and 
northern regions ; and 
III. In medicine, as substitutes for various expensive nutrients, 
demulcents, tonics, antiperiodics, or astringents. 
In some of these forms they have been of no insignificant 1m- 
portance, directly as well as indirectly, to man. These uses or 
applications to the necessities or comforts of man have been 
founded on their capability of yielding the following products, or 
on their possessing the following substances, viz. :— 
I. Colorific Substances. 
a. Colorific principles, such as Orseliic, Hrythric, Lecanoric, 
Gyrophoric, or iHverine acids, capable of yielding, by the joint 
action of atmospheric air, water, and ammonia, a red or purple 
colouring matter, of which Orchill, Cudbear, and Litmus are 
merely varieties depending upon the mode of manufacture. This 
is the rationale of the production of the “Orchill” of Eng- 
land, “‘ Cudbear” of Scotland, “ Litmus” of Holland, “ Orseille 
d’Auvergne” of France, “ Beettelet” of Sweden, “ Korkalett” 
