274 DR. LAUDER LINDSAY ON ABTHONIA MELASPEEMELLA. 



and as stylospores^ — the latter being almost invariably larger, 

 broader, more irregular in form, sporoid in their aspect, frequently 

 granular, occasionally coloured, and sometimes septate. 



I have found similar pycnides and spermogones (including tri- 

 ple forms of the latter in a single species) in the genus Opegrapha. 



Certain other Arthonicd resemble A. melaspermella in the pos- 

 session of lecideiform or patellarioid apoihecia : such are A. tra- 

 chyloides^ Nyl., in which Mudd points out this peculiarity in its 

 physiognomy* ; A. macrotheca, Fee, from Guyana, in the Hookerian 

 Herbarium, Kew; and-4. melaleuca^ Nyl. In such forms there has 

 been no little confusion between certain species of Arthonia and 

 of the genus Lecidea: E. g., forms of Lecidea parasema^ Ach., var. 

 punctata^ Ach., have been confounded Avith Arthonia patellulata, 

 Nyl.; Lecidea dryina^ Echb. Exs. 71, is Arthonia melaleuca, Nyl., 

 which moreover resembles A. melaspermella in having brOAvn, and 

 one- (though sometimes also two-) septate spores ; A German 

 specimen in the Hookerian Herbarium, Kew, variously labelled 

 Lecidea dryina^ Ach., Coniangium vulgare, Fr., and Spiloma para- 

 doxum^ Ach., appears referable to Arthonia lurida, Ach. ; Arthonia 

 lurida^ Ach. var. glolularis^ Ach., is Lecidea glohilaris, Nyl. 

 Lich. Scand. 213, its hymenial gelatine striking a blue with iodine. 



The reaction with iodine of the hymenial gelatine in the genus 

 Arthonia varies from deep and beautiful blue to the faintest shades 

 of wine-red, being reddish or violet in the majority of species 

 found it more or less deep blue (for instance) in A. macrotheca, 

 F^e, A. minutula^ Nyl., A. dispersa, NyL, and A. asfroidea, Ach. 

 from Ireland (thecae only), all in the Hookerian Herbarium. 

 It is also intensely blue in A. minutissima, Nyl.t 



The genus Arthonia, as at present established, is a large and 

 heterogeneous one, comprising species formerly referred to the 

 following old or existing genera : 



I 



I. Lichens, 



1. Graphis, Adans, 



2. Opegrapha, Humb, 



3. Lecanactis, Eschw» 



4. Leprantha, Duf. 



5. Coniocarpon, DC. 



6. Coniangium, Fr. 



7. Spiloma, Ach. 



8. Pachnolepia, Mass. 



9. Arthrothelium. Mass 



Manual 



I 



10. Parmelia, JcA. 



11. Lecaaora, JcA. 



12. Lecidea, Ach. 



13. N«via, Fr. 



14. Trachylia, Fr. 



15. Verrucaria, fVigg- 



16. Limboria, Ach. 



17. Pyrenotbea, Fr. 



18. MyTiangiuin,2>Mr.4'Jlfa«/ 



t Lich. Scand. 263. 



^ 



I 



X' 



