nded use of the lichens as dye agents. What renders it
very probable that efforts in this direction are likely to meet with
success is the great similarity of species found all over the world.
It has been repeatedly noticed that the European species, which, of
course, are best known, differ little from those of North America.
Dr. Robert Brown remarked the same fact with regard to New Holland
species, and Humboldt also recognised the similarity in natives of
the South American Andes. Of a large collection made by Professor
Royle, in the Himalayas, Don pronounced almost every one to be
identical with European species. From examining the raw vegetable
products, sent by different countries to the Great Exhibition of
1851, I am satisfied that, even now, there are many fields open for
the establishment of an export trade in _Roccellas_ and other
so-called orchella weeds." I there saw specimens of good dye lichens
from almost every part of the world, including our own young
colonies; and as a single instance of their probable value, I may
introduce here the copy of a note appended to a specimen of orchella
weed from the island of Socotra, contained in the Indian collection
of that exhibition, "_abundant_, but _unknown_ as an article of use
or commerce. Also abundant on the hills around (Aden) and _might_ be
made an article of trade." Roccellas from this source are estimated
as worth L190 to L380 per ton. I believe that a similar statement
might be made with regard to the countless islands of the broad
Atlantic and Pacific, which may, at some future period, perhaps not
far distant, be found to be rich depots of orchella weeds, just as
some of them are, at present, rich fields of guano, and may, as
such, become new nuclei of British commerce and enterprise. Even at
home, in the immediate vicinity of Edinburgh, or, to restrict our
limits still more narrowly, within the compass of Arthur's Seat,
there are not a few very good dye-lichens, which require merely to
be scraped with an old knife or similar instrument, from the rocks
to which they adhere, and subjected to the ammonia process already
mentioned. Of twelve specimens thus collected at random one morning,
I found no less than three yielded beautiful purple-red colors,
apparently as fine as orchil or cudbear, while the others furnished
rich