1870.] Dr. J. Stcnliouse on certain Lichens. 227 



salt. The acid when freed from lime and purified, melted at 20 2° C, and 

 by analysis gave the following results : — 



I. '409 grm. usnic acid gave '939 grm. carbonic anhydride and '188 

 grm. water. 









L 





= 216 



=» 62-43 



62-63 



H 18 



= 18 



= 5-20 



5-11 



o 7 



= 112 



= 32-37 







346 



100-00 





From the above analyses it will be seen that the usnic acid from Evernia 

 prunastrih identical in composition with that from Vsnea barbate/. It has 

 the same melting-point, and agrees with it in all its other properties. 



Cladonia rangiferina. 



In 1848* I extracted the lichen acid from Cladonia rangiferina, and 

 by analysis found it to have the same composition as usnic acid, with which 

 it agrees very closely in its properties. Hesse, however, observedf that 

 this acid had a different melting-point (1/5° C.) from ordinary usnic acid 

 (203° C), and proposed, therefore, as it so closely resembled ordinary 

 usnic acid in its general character, to call it /3-usnic acid. 



Cladonic Acid, p-orcin. 



I formerly obtained^ /3-orcin by subjecting to destructive distillation a 

 mixture of the acids from Cladonia rangiferina and various species of Vsnea; 

 but I have lately found that ordinary usnic acid, melting at 203° C, ob- 

 tained from Evernia prunastri, Ramalina calicaris, and the various Vsneas, 

 does not yield a trace of /3-orcin when distilled, whilst, ou the contrary, 

 the acid extracted from Cladonia (Hesse's /3-usnic acid melting at 175° C), 

 on being subjected to the same treatment, yields /3-orcin, thus showing a 

 marked difference in the products of its decomposition from ordinary usnic 

 acid, as well as in its melting-point. Under these circumstances, therefore, 

 I think that it would be better to name the acid from Cladonia rangiferina 

 " Cladonic Acid," instead of /3-usnic acid, as proposed by Hesse. 



I expected to have been able to subject cladonic acid to a more careful 

 examination, and procured for that purpose a quantity of Cladonia rangi- 

 ferina from the neighbourhood of Moffat. Unfortunately, however, it was 

 not gathered until the beginning of December, and I was surprised to rind 

 that it contained scarcely a trace of cladonic or any similar acid. I intend 

 to obtain a new quantity next summer, when I hope to be more successful. 



I cannot conclude this paper without acknowledging the efficient assis- 

 tance I have received from Mr. Charles E. Groves. 



* Ann. der Chem. und Pharm. vol. lxyiii. p. 93. 

 t Ibid. vol. cxrii. p. 347. 

 \ Ibid. vol. kviii. p. 104. 



