DESCRIPTION OF THE PLATES. 



8. S. fuliginosa, upper surface, showing the soot- coloured 

 powder of the margin. 



9. Ditto, under surface, showing the white cyphellse. 



PLATE XII. 



1. Parmelia pulverulent a. 



2. Ditto, section of thallus, showing rhizinse of under surface, 

 magnified. 



3. Ditto, section of apothecium, magnified. 



4. Ditto, apothecium, showing its pruinose character. 



5. Ditto, spore. 



6. Parmelia saxatilis, furfuraceous variety. 



7. Ditto, section of thallus, showing the rhizinse of the under 

 surface. 



8. Ditto, section of apothecium. 



9. Ditto, spores of var. omphalodes. 



1 0 . Parmelia parietina . 



11. Ditto, portion of thallus magnified, showing marginal 

 spermogones. 



12. Ditto, section of apothecium, magnified. 



13. Ditto, apothecium, magnified, common form. 



14. Ditto, ditto, cephaloid or symphycarpeous form, 



15. Ditto, vertical section of spermogone* 



16. Ditto, sterigmata and spermatia. 



17. Ditto, spore under action of iodine. 



18. Parmelia amplissima, spore. 



