38 DK. LAUDEB LINDSAY OK CHEMICAL EEACTION 



Th. M. Fries "has endeavoured in his later works * to apply all 

 tlie reagents recommended by Nylander and Leigliton, including 

 iodine, to the medullary tissue of the Lecidece. Stizenberger has 

 supported Nylander's views f ; and there seems at present a general 

 tendency among continental lichenologists to introduce into their 

 descriptions of species the actions of one or all of the reagents 

 which are supposed or asserted to possess such important uses 

 in diagnosis. 



Nylander, however, does not limit the usefulness of the chemi- 

 cals he introduces to the mere diagnosis of species. He appears to 

 regard them also, in some instances at least, as colorimetric 

 tests, — as, for instance, when he says of Hoccella " Thus are we en- 

 abled to say what is the quantify of this colorable matter which 

 the different species of the genus contain, it being in fact a sort 

 of immediate analysis " (p. S59), or of Parmelia *' Most of them 

 contain more colorable matter than the best i2occeZZ<^ " (p. 361) J - 



The following are the chief reactions described by Nylander : 



I. With hypochlorite of calcium. 



ErytTi7n7iic = ti fugitive red. 



II. "With hydrate of potash. 



A, ChrysopTianic = r permanent ^uv^\e. 



B. TJsnic = n pennanent yellow or greenioh jeWow. 



c, A fugitive yellow, changing quickly to red — to which reac- 

 tion he does not give a special name or associate it with 

 the presence of a special colorific. principle. 



The erytJirinic reaction, which is typically developed in the 

 genus Boccella, he appears to attribute to erythric acid. The 

 clirysophanic reaction, which is typically developed in the yellow 

 IBhyscice and Placodia, he attributes to the presence of chrysopha- 

 nic acid. The usnic reaction, which is typically exhibited in the 

 genus Cladonia, he associates with the occurrence of usnic or leca- 

 noric acids. The third group of potash reactions is typically 



Lecanora cinerea § 



* E.g. •' 



Handlingar 



■Atademiens 



Botanische 



1867, p. 151. 



J This assertion is quite opposed to the eij^riencc of archil-manufacturers, 



who Iiare, in this country at least, giyen up theuse of the ParmeluB in favour of 



the EocceU(B [vide the autlior*s paper in the * Brit. Assoc. Report,' post, citat,]^ 



§ I am far from satisfied of the propriety of the terms here employed by 



