DR, LIXDSAT ON THE LIClIEIf-FLORA OF KORTITKRl!?- EUROPE. 3G5 



afterwards of a red, almost purple colour. Very nearly the same 

 reaction is visible in Lecanora ocJiroidea, Ach. (Meth. p. 72, sub 

 Lecidea) ; but ordinarily its thallus treated with the potash re- 

 mains yellow, and tlie red colour appears only on tlie thalline 

 margin of the apothecia, thus causing the disk to be surrounded 

 with an elegant red ring. I have distributed the ochroidea in my 

 Herb. Lich, Paris. 41. 



These examples arc amply sufficient, I think, to point out the 



invaluable aids afforded by chemical reactives in tlie study of 

 Lichens* 





Contributions to the Lichen-flora of ]S"orthern Europef. ByW. 



Lai'der Lt^dsat, M.D,, IMl.S. Ed., E.L.S^ etc. 



With a view to extend and improve my knowledge of the varia- 

 tions of those Lichen-species which are natives of Scotland, as 

 well as to add to my Lichen-herbarium, I visited, in the summer 

 of 1857 (August) the Norwegian Alps, and in that of 1800 (June) 

 Iceland and the Euro Islands. AVhile not neglecting the higher 

 and larger lichenSj which iu all these countries have long been 

 comparatively well known, and which are easily determinable, for 

 the most part or altogether, by nalced-eye characters, I devoted 

 myself chiefly to the collection of the more obscure and minute 

 lower lichens — crustaceous or athalline, terricolous, saxicolous, 

 and muscicolous species — which are less perfectly or little known, 

 and which require for their determination the assistance of the 

 microscope, and access, for comparison, to the largest and best 

 lichen-herbaria and lichenological libraries. 



Of Icelandic lichens, the latest list, as far as I am aware, is 

 that published by myself in 18G1 J. It is a compilation which in- 

 cludes the lists of all previous authors : but their nomenclature is 



The analyses of Lichens made by chemists often fail tlirongh tHc neglect 

 of an exact determiuation of the species, and probably not less often by the 

 future of specimens confomided together and incorrectly assigned to one single 

 species. For instance, that which Eobiquot has called ** Varlolarla dealbata,^ 

 and from wJiicIi he lias extracted orcuief is not the Lichen dealhalus oi Acharius, 

 "whicli does not contain tliis matter, but is probably Lecanora tartarea or 

 pnllescensy or even Urceolaria scruposa^ or all these and others intenuixed. 

 -Por the chemist, no less than for the physiologist, it is of the greatest import- 

 ance to know exactly what is the plant we have under observation — that is, to 

 have Well determined the plant which we are studying. 



t Being an enumeration of Lichens collected iu Iceland, the Faro Islands, 

 and Norway, in 1857 and 1860. 



X In the " The Flora of Iceland," Section Licliem : Edinb. New Philosophy 

 Journal, July 1861. 



