25 
EXPERIMENTS ON THE COLORIFIC PROPERTIES 
OF LICHENS. 
By W. Lauder Lindsay, M.D., F.R.S.E., F.L.S. 
The subject of the colours or colouring matters contained in, or 
educible from, Lichens — to which I directed attention about 25 
years ago* * * § — has recently re-acquired considerable interest or im- 
portance in connection with, or in relation to, 
1. The Introduction of Colour- tests, as characters for species in 
Lichens ;f 
2. The development of fast dyes from Lichens , capable of com- 
peting successfully with the coal tar and other recent pro- 
ducts of the chemist’s laboratory and 
3. The continued domestic use of Lichens as Dye-stuffs in 
our own country. § 
So long ago as 1853, || in connection with an experimental in- 
quiry on the economical applications of the Lichen-dyes, I pointed 
out the extreme unsatisfactoriness of our knowledge of the Chemistry 
of these dyes ; and the progress of science in this direction has 
not since been such as to enable me to modify the strong opinion 
then expressed.^]" During the last 25 years the principal changes 
in our knowledge of the chemistry of these colouring matters con- 
sist in — (1) the addition of sundry (supposed or really) new sub- 
stances, which addition confuses to a still greater degree the 
previous confusion of names ; and (2) certain proofs of the correct- 
ness of an opinion I was long ago led to hazard, that several, at 
least, of the bodies described by different chemists as differing 
trivially in constitution or characters, would prove to be referable 
to the same substance.** I have more than once pointed out the 
necessity that exists for a new series of researches on the chemistry 
of the Lichen-colouring matters, to be undertaken conjointly by 
* “ Experimental Researches on the Tinctorial Properties of Lichens.” 
Proceedings of Botanical Society of Edinburgh, 1853-4-5 ; “ North British 
Agriculturist,” 1853-4; “ Phytologist,” 1853-4; ‘‘Edinburgh New Philoso- 
phical Journal,” 1854-5. 
f “ Chemical Reaction as a Specific character in Lichens.” “ Journal of 
Linnaean Society, Botany,” vol. xi, p. 36. 
X “ Present nses of Lichens as Dye-stuffs.” Report of British Association, 
1867 ; Transactions of Sections, p. 40 ; Seemann’s “ Journal of Botany,” 
vol. vi (1868), p. 101. 
§ “ Present domestic use of Lichen Dye-stuffs in the Scottish Islands 
and Highlands.” Seemann’s “ Journal of Botany,” vol. vi. (1868), p. 84. 
|| “ Phytologist.” Yol. iv. (1854 ), p. 905. 
“ Lichen Dyes.” Hardwicke’s “ Science Gossip,” December, 1867, 
p. 266 ; and paper on “ Present uses of Lichens as Dye-stuffs ” (supra citat). 
** In his latest contribution to Lichen- Chemistry, Stenhouse (“ On some 
Varieties of Orchella Weed and the products obtained from them” — 
“ Journal of the Chemical Society,” May, 1867) admits that his Erythric 
acid is the same as Schunck’s Lecanoric acid. 
3 
