of Edinburgh, Session 1869-70. 
43 
Monday , \lth January 1870. 
GEORGE ROBERTSON, Esq., Councillor, in the Chair. 
The following Communications were read: — 
1. Experiments on the Colorific Properties of Lichens. By 
W. Lauder Lindsay, M.D., F.R.S.E., F.L.S. 
The author’s paper consists mainly of a Table exhibiting certain 
of the positive results of many hundred experiments on the colour- 
ing matters contained in or educible from Lichens. The experi- 
ments in question are partly a repetition, and partly an extension 
on a more systematic and complete scale, of a series of researches 
made by the author between 1852 and 1855, the results of which 
were originally submitted to the Botanical Society of Edinburgh. 
The present series of experiments includes the whole family of the 
Lichens. The Table represents mainly the effects of chemical re- 
agents on solutions of the lichen colouring-matters, or colorific 
principles, in boiling alcohol or water. The nomenclature of the 
Colour-reactions is that of Werner and Syme. As the subjects of 
his experiments, the author confined himself in great measure to 
the lichens contained in published Fasciculi; so that comparative 
experiments may hereafter be made on authentic specimens of the 
same species and varieties by other observers in other countries. The 
author’s results are submitted as a mere pioneer contribution to a 
subject, which has been as yet most imperfectly worked out, viz., 
the Chemistry of the lichen colouring-matters ; but he trusts they 
may furnish a partial basis for a future more exhaustive series of 
researches to be undertaken conjointly by Chemists and Lichenologists. 
The present Table illustrates pro tanto — 
I. The kinds of colour producible from lichens : those, viz. — 
(а) Which exist ready formed in the thallus — for the most 
part green, yellow, or brown, — and which are of little 
practical utility ; and 
(б) The colourless colorific principles, which, under the action 
of ammonia and atmospheric oxygen, yield red or purple 
