100 Rev. "W. A. Leighton on the Cladoniei 



Having recently, through the kindness of the learned Director, 

 Dr. Hooker, had an opportunity of thoroughly examining the 

 extensive collection of Cladoniei in the Hookerian herbarium at 

 Kew, I have had ample means of applying these tests, and now 

 proceed to make known the results. 



This valuable collection comprises the herbarium of the late 

 Mr. Dawson Turner (which contains various authentic specimens 

 received from Dr. Acharius himself), the herbarium of the late 

 Mr. Borrer (which is kept separate), and a large general collec- 

 tion from all portions of the globe. 



The Acharian specimens (like all those which I have seen 

 elsewhere) are mere scraps, and scarcely merit the character of 

 herbarium specimens, though highly valuable and interesting 

 as relics of the great father of lichenology, and remarkably 

 useful and sufficiently satisfactory in aiding us to a knowledge 

 of the particular plants meant by this distinguished author. 



The Borrerian herbarium contains better and larger specimens 

 of our British Cladoniae ; but, from the circumstance of various 

 different species being found intermingled under similar names, 

 it is often exceedingly difficult to ascertain what precise ideas 

 this acute and observant lichenist really possessed concerning 

 these lichens. 



The same intermingling was also remarked throughout the 

 large general collection. 



The value of the chemical tests in furnishing us with addi- 

 tional and confirmatory specific characters becomes at once 

 plainly manifest, inasmuch as it facilitates the arrangement of 

 specimens under their proper species, which the intelligent ob- 

 servation and skill of Acharius, Turner, Borrer, SirW. J. Hooker, 

 Churchill Babington, Dr. Nylander, and others, depending on 

 external characters and aspects alone, have failed to effect. Not 

 that it is desired to depreciate in the slightest degree the 

 learning and acuteness of these giant intellects, who must ever 

 command our deepest veneration and respect, but rather to evi- 

 dence by these facts the real utility and value of these chemical 

 tests. 



The following is the reaction observable in, and the determina- 

 tion of, the specimens received from Acharius himself in the 

 herbarium of the late Mr. Dawson Turner, preserved in the 

 herbarium at Kew : — 



'^ csespititia," K— C— , true. 



" strepsilis,^^ K— C— , like a state of sobolifera, Del. 



" alcicornis," K — C + , true. 



" endivi^folia," K f+ C-f , true. 



