DESCRIPTION OF THE PLATES. 



xiii 



6. Ditto, two of these cilia greatly magnified, showing the 

 spermogones. 



7. Ditto, spermogone still more highly magnified. 



8. Ditto, sterigmata and spermatia. 



9. Ditto, spore. 



10. Spore of Cetraria juniperina. 



11. Cetraria nivalis. 



12. Ditto, magnified, showing black-punctate margin. 



13. Medullary tissue of Peltigera venosa. 



14. Ditto, P. liorizontalis. 



15. Cortical cellular tissue of ditto. 



16. Medullary filament of ditto, under the action of iodine. 



PLATE IX. 



1. Peltigera canina, upper surface. 



2. Ditto, under surface, showing veins and rhizinse. 



3. Ditto, margin of thallus, showing spermogones and nascent 

 apothecium. 



4. Ditto, marginal spermogone magnified. 



5. Ditto, vertical section of spermogone magnified. 



6. Ditto ditto, much more highly magnified, showing sterig- 

 mata and spermatia. 



7. Ditto, sterigmata. 



8. Ditto, spermatia, isolated. 



9. Ditto, spore. 



10. Peltigera horizontalis, section of young apothecium. 



