36 DE. LAUDER LINDSAY 01^ CHEMICAL REACTTO^" 



On Chemical Eeaction as ajSpecific Character in Lichens. By 



W. Laudeb LtniMat, M.D., T.E.S.E., &c. 



[E^ad November 19, 18G8.] 



Contents. 



1, Summary of obseiTations by Ny lander and Leighton on 



Erythrinic, 



Chrysophanic, and \ reactions, with their subactions 



Usnic 



2, Criticism on said observations. 



3. Summary of author s observations on the reactions of 



a. Chlorinated lime and soda, 

 h. Potash and ammonia, 



c. Iodine, 



i. Directly, on 



surface 



(6) The^ir internal tissues- 

 ii. On alcoholic or aqueous decoctions of thallus. 



DuEiNG the last few years several Lichenologiata* of established 

 reputation have introduced what they are pleased to call new 

 criteria"* or "new chemical tests" in the study of Lichens 

 — chemical characters, in short, for the differential diagnosis ot 

 species. They have done so, moreover, in language so sanguinCj 

 and with assertions so strong, that, if their observations could be 

 substantiated as facts, their generalizations could not fail to be oi 



Lichenology 



introducing 



Hydrate 



species in certain large and important groups, families, and genera, 



in the following terms f : 



" These examples are amply sufficient, I think, to point out the 

 invaluable aid affordedby chemical reactives in the study of Lichens 

 (p. 365). « By these examples, which may be verijled ttnti 

 the greatest ease, I believe that I have sufficiently estaUished the 



hypochlorite 



Their 



Feb- 



ruary 1867, ** I quite agree that much light may be thrown on the hotans 



of Lichens by means of chemical reaction." I cannot, ho-wever, accept the tes 

 mony of a chemist on a question of botanical diagnosis. 



t ** Ilypochlorite of Lime and Hydrate of Potash, two new Criteria in the stu J 

 of Lichens," Journal of the Linnean Society, Botany, vol. ix. p. 358. Vide dX^ 



tests 



ToL xviii. p. 169. 



Leighton, Annals of Natural History, ^^ 



