52 DB. LAUBEK LINDSAY ON CHEMICAL KEACTION 



P. oUvetorum ; but I have no reason to suppose that in this ease, 

 exceptionally, chemical reaction furnishes a character sufficient of 

 itself to separate or constitute species. Perlata^ like saxatilisy is 

 an instance of a long-known and widely used dye-lichen [capable 

 of yielding archil], which gives, as a rule, no reaction with 

 bleaching-solutiou. ' , 



G-enus Vmhilicaria, — Ny lander asserts that the medulla of 

 most of the Vmhilicariw exhibits an erythrinic reaction (p. 3G2). 

 He admits, however, that in the same species [e. g. hyperhored] 

 the reaction may be obscure or distinct, and that in this and other 

 species of the genus it may be better exhibited in yoimg specimens 

 than old. The result of my testings of a large suite of specimens 

 in my herbarium is that it is only exceptionally, after much 

 friction, and faintly that an erythrinic reaction is developed at 

 alL Nylander's statement, that there is only " a small quantity 

 of colourable matter which is to be found in them," is opposed to 

 the experience of archil-manufacturers, who at one time, if not 

 still, used, or use, one or more species as dye-lichens [JJ. pustitlata 

 and Z7. murina]^, • 



II. Reaction with Potash. - A. Chrysophanic, — In lichens whose 

 colour is yellow, orange, or red, the seat of colour is, according to 

 Leighton, following Nylander, a " powder .... generated on the 

 surface " of the thallus or apothecla. I have not given speciul at- 

 tention to this subject ; but it seems to me extremely unlikely that 

 colouring-matter should not, in these as in other lichens, reside m 

 the cells or filaments, or intercellular matter, of the cortical or 

 j^aeduUary tissues f. There may be, and frequently is, an efflores- 

 cence of granular colouring-matter (just as I believe there is of 

 colorific principles iu a crude form) in lichens, where such matters 

 or principles exist in, or are secreted or excreted by, the thallus. 

 But it does not appear to me that Nylander's and Leighton's 



colour 



correct. 



Tlio development of a purple reaction in apothecla which are 

 naturally of a deep red is generally obscure, if it exists at all, and 

 cannot, so far as I can see, serve any good purpose in cla^sifica- 

 .tion, e. g. in tlie erythrocarpous Lecanorw and Lecideod {^Lecanora 

 JKBinatomma and V€ntosa\' In no lichen is the colouring-matter 



* Vide author's paper, '*0n the Dyeing Properties of Lichens/' Edin. N'e\«' 

 Philos. Journal, July 1855, Table ii. 



t Vide section on Co^mr in author's ' British Lichens ' (1856), p. 47. 



