122 Rev. W. A. Leiuliton on the Genus Ramalina. 



't> 



XNl.—NotuJce Lichenologicce. No. XXXV. 

 By the Eev. W. A. Leighton, B.A., F.L.S., F.B.S. Ed. 



Recognitio MonograpMca Ramalinarum. 8cripsit 

 William Nylandee, Caen, 1870. 



Dr. W. Nylander has published, in the ' Bulletin de la 

 Soci^t^ Linn^enne de Normandie,' ser. 2. t. iv., and also sepa- 

 rately, a very valuable monograph of one of the most difficult 

 genera of Lichens, Ramalina. In respect of difficulty and 

 uncertainty the genus Ramalina is amongst lichens analogous 

 to the genera Rubus and Hieracium amongst flowering plants. 

 The critical acumen and painstaking discrimination of Dr. 

 Nylander have now, however, placed in our power the clue to 

 this puzzling labyrinth. In effecting this, Dr. Nylander has 

 discovered that the differences of the external surface of the 

 receptacles of the apothecia, and also the form and size of the 

 spores and spermatia, which have been hitherto altogether 

 neglected or overlooked, do in reality afford useful essential 

 characters. To these must be added the chemical reactions 

 resulting from the application of hydrate of potash to the 

 medulla, which in one species is tinged with yellow, or yellow 

 which soon changes into red, whilst in other species no reac- 

 tion is produced. '' Medullam eo adminiculo tum crocee vel 

 lateritio-rubricose vel sanguinee tingi (prascedente tlavescentia), 

 apud alias vero species nullam talem coloris mutationem ob- 

 servavi." He cautions students that this reaction is instanta- 

 neous or nearly so, and that the discoloration resulting from slow 

 drying or a secondary and slow reaction is to be altogether dis- 

 regarded. " Beactionem ejusmodi dico eam, quai applicato 

 adminicido chcmico mox vel fere mox prodit, nee respicio 

 colorationem obscuram interdum desiccatione lente accedente 

 ortam vel sccundariam et tardam." 



With regard to chemical reactions generally, I may take 

 this opportunity of mentioning that different observers have, 

 according to their statements, not unfrequently obtained dif- 

 ferent reactions from those indicated by writers on this sub- 

 ject. This may probably be accounted for in several ways. 

 Either the experimenter has relied entirely on the supposed 

 accuracy of the labels attached to specimens in published 

 Exsiccati, without also ascertaining, by examination into 

 essential characters, whether the lichen be really that indicated 

 by the label or not ; or the chemicals used were old or feeble, 

 or had become wanting in energy by exposure to the atmo- 

 sphere. Both of these would be sources of error, and hence 

 also different results. My own experience induces me to re- 

 gard as of essential importance that the chemicals be of the 



