50 PB. LAUDEB LINDSAY OK CHEMICAL HE ACTION 



brilliant. Corticolous specimens of pallescenSy from Cork (1858), 

 also gave the blood-red of tartarea. Notwithstanding all that has 

 been written on the subject of their chemical distinction by Ny- 

 lander and Leighton, I see no reason to modify the opinion 1 

 formed many years ago from their structural resemblances, that 

 tartarea and parella, with all their varieties or intermediate 

 forms, are referable to a single type. 



Stizenberger describes the " schwer zii bestimmende Pertmaria 

 velafa^^ of Switzerland as " leicht an ihrem Erj^thrinsaure-Gehalt 

 kenntlich "* — a statement that is opposed to the fact that in two 

 specimens (variolarioid and degenerate) from Otago, N. Z., I ob- 

 tained no reaction ; while in a third, which was fertile, a beau- 

 tiful blood-red was developed — all three specimens having been 

 named by Nylander. 



Grcnus Parmelia, — " It is perhaps in the ParmelicB,^^ says Ny- 

 lander (p. 361), " that the erythrinic reaction presents the most 

 remarkable advantage as the means of distinguishing between 

 those species which differ very little in external appearance. In 

 reality the colourable material in the Parmelite is found under- 

 neath the gonidial layer, and not upon it or in its exterior as is 

 the case in the Boccellce, Consequently it is necessary to cut 

 the thallus of a Parmelia, so as to expose the medulla, whenever 

 we wish to ascertain whether the species exhibits the erythrinic 

 reaction or not on the application of the hypochlorite of lime." 

 Leighton says the seat of reaction in lichens is a " colourable ma- 

 terial which is generated in the gonidial stratum of the thallus,** 

 d most unlikely source ; but he goes on to give directions for 

 scraping off the cortical layer of Parmelia, and all lichens with a 

 cortical layer, "to expose the subjacent medulla, in which the 

 reaction takes place'* — another of Leighton's confusing or con- 

 tradictory assertions. The truth is, that the seat of colorific 

 material in lichens is partly the cortical, partly the medullary, 

 thalline tissues, and partly those of the apothecium- 



Nylander asserts that there is no erythrinic reaction in the 

 common P. iaxatilis ; nor did I find it, as a general rule, in a 

 large suite of specimens in my herbarium. But in one specimen, 

 from Maine, U. S. A. (1867), bleaching-solution developed at 

 once, on gentle friction, in the medulla, one of the most beautiful 

 and deep blood-reds I have ever obtained with this reagent among 

 lichens. It is an excellent illustration of the marked difiFerence 



* '^ 



* Review in the * Botanische Zeitung/ 1867, p. 151. 



