LICHENS. 487 



The subject of the colorific and coloring principles of the lichen has, within 

 the last few years, attracted a due share of that attention which has been in- 

 creasingly devoted to organic chemistry. Since 1830, Heeren, Kane, Schunck, 

 Rochleder and Heldt, Knop, Stenhouse, Laurent and Gerhardt, have published 

 valuable papers on these principles ; but, here again, we have to regret the 

 great discrepancy in the various results obtained, and there is therefore, here 

 also, imperatively demanded re-invostigation and correction before any of the 

 results already published can be implicitly relied upon, and before we can have 

 safe data from which to generalise. I have no doubt that a great proportion of 

 the obscurity overhanging this subject depends on the circumstance that many 

 of the chemists, who have devoted attention to the color-educts and products of 

 the lichens, were not themselves botanists, and have therefore probably, in 

 some cases at least, analysed species under erroneous names, and also because 

 their investigations have comprehended a much too limited number of species. 



Their utility in the arts, and especially in dyeing including the collection. 

 of a series of the commercial dye lichens, i.e., those used by the manufacturers 

 of London, &c., in the making of orchil, cudbear, litmus, and other lichen dyes. 

 While investigating the dyeing properties of the lichens, I made experiments, 

 with a view to test their colorific power, on as many species as I could obtain 

 in sufficient quantity, to render it at all useful to operate on that number, 

 however, being very limited (between forty and fifty). 



Dr. Lindley adds, many parties may be able to aid his investigations, by fur- 

 nishing information on their economic uses, and on their special applications in 

 dyeing and other arts (particularly on their employment, as dye agents, by the 

 natives of Britain and other countries) with specimens of the lichens so used, 

 and their common names specimens of fabrics dyed therewith notes of 

 the processes employed for the elimination of the dyes, &c. Parties resident 

 in, or travelling through our western Highlands and Islands, the northern 

 Highlands, Ireland, Wales, Norway, Iceland, and similar countries, are most 

 likely to be able to afford this description of information many native lichens 

 being still used by the peasantry of these countries to dye their home-spun 

 yarn, &c. 



He proceeded to treat 1. The vast importance of this humble tribe of 

 plants in the grand economy of nature, as the pioneers and founders of all 

 vegetation. 2. Their importance to man and the lower animals, as furnishing 

 various articles of food. 3. Their importance in medicine, and especially in its 

 past history, at home and abroad, 4. Their importance in the useful and fine 

 arts, and especially in the art of dyeing. 5. Their affinities and analogies to 

 other cryptogamic families, and to the Phanerogamia. 6. Their value as an 

 element of the picturesque in nature ; and, 7. Their typical significance. 



He then adverted more especially to the subject of his communication, under 

 the ten following heads : 



I. The colors of the Thallus and apothecia of Lichens their causes, and 

 the circumstances which modify and alter them. 



II. History of the application of their coloring matters to the art of dyeing. 



III. Chemical nature and general properties of these coloring matters. 



IV. Tests and processes for estimating qualitatively, and quantitatively the 

 colorific powers of individual species with their practical applications. 



V. Processes of manufacture of the Lichen-dyes, on the large and small 

 scale in different countries with the principles on which they arc founded. 

 VI. Nomenclature of the dye-Lichens, and of the Lichen-dyes. 

 VII. Botanical and commercial sources of the same. 

 VIII. Special applications of the Lieheu-dyes in the arts. 

 IX. Commercial value of the dye-Lichens, and their products. 

 X. Geographical distribution of the dye-Lichens with the effect of climate, 



situation, &c., on their colorific materials. 



Of the four first sections of his paper, the following is a very short summary 

 or synopsis : 



Under the first head, the author spoke of chlorophylle and various organic 

 and inorganic substances, which enter into the formation of the colors of the 

 thallus and apothecia of lichens, and of the modifications of these colors de- 

 pending on various degrees of 1. Exposure to air and light. 2. Temperature. 



