1009 



scientifically interesting; but it may come to be an important matter, 

 in a pecuniary point of view, to discover, at home or abroad, some 

 cheap and easily procurable substitutes for the Roccelias, which are 

 rapidly becoming scarce, and consequently valuable, in European 

 commerce. The results of my experiments are not so satisfactory as 

 I could have wished, owing to the comparatively small number of 

 fresh specimens operated on ; still, I think, they will sufficiently indi- 

 cate that we have in Scotland a large number of species capable of 

 yielding excellent colouring matters, in every probability capable of 

 supplanting, or vieing with, the Lecanoras, Gyrophoras, Umbilicarias, 

 &c. (which are at present largely collected in Norway and Sweden 

 for the London market), or even with the Roccellas. It is not for me, 

 at present, to say on what chemical changes the various re-actions I 

 have laid down depend ; whether all, or how many, of these colours 

 can ever become serviceable to the dyer, or otherwise, and, if so, by 

 what processes. These and similar questions I leave it for the che- 

 mist, dye-manufacturer, and dyer to decide ; meanwhile, merely indi- 

 cating facts. 



" The greater number of the lichens operated on are herbarium spe- 

 cimens, collected, several years ago, in various parts of Switzerland, 

 Scotland, and the Vosges district ; a few are natives of Norway, Ger- 

 many, and other foreign countries. 



" The re-agents used for the development of colour are only 

 intended to be applied to those, lichens which contain colourless 

 principles, capable of conversion, by chemical raetamoi*phoses, into 

 coloured substances. They are chiefly adapted to the evolution of a 

 red colour, which is the most important yielded by the lichen family. 

 Where the thallus contains abundance of colouring matters ready 

 formed, these are soluble in almost any fluid ; and ammonia or hypo- 

 chlorite of lime have not a more specific action on them than water. 



" In order to attain some degree of uniformity in the nomenclature 

 of the colours obtained in these experiments, especially those pro- 

 duced by ammoniacal maceration, I have designated the more marked 

 tints according to Werner's celebrated nomenclature of colours, as 

 contained in the little work edited by Syrae. 



" In the ' Table of Experiments,' the 1st column contains the 

 botanical name, and, in many cases, the synonym, of the lichen ope- 

 rated on. 



" The 2nd column contains generally the country of which the plant 

 is a native, and more particularly the nature of its habitat. 



"The 3rd column contains the date of collection of the plant. Tt 

 VOL. IV. 6 X 



