DESCRIPTION OF THE PLATES. XXV 



10. Ditto, isolated spores. 



11. Ditto, sterigmata and spermatia. 



12. E. lachneum, section of thallus and two spermogones. 



13. Ditto, spores germinating. 



14. Ditto, sterigmata and spermatia. 



15. Ditto, free spermatia. 



16. U. sorediatum, spores full and empty. 



17. Chiodecton albidum. 



18. Ditto, portion of thallus, magnified, showing the relation 

 of the spermogones, a s to the apothecia, b. 



19. Ditto, vertical section of an apothecium. 



20. Ditto, transverse ditto. 



21. Ditto, section of thallus, showing portion of an apothe- 

 cium, and a spermogone, b. 



22. Ditto, spore. 



23. Ditto, spermatia. 



PLATE XXI. 



1. Pertusaria communis, showing zonate condition of young 

 thallus. 



2. Ditto, variolarioid degeneration of apothecia. 



3. Ditto, apothecial warts, magnified. 



4. Ditto, transverse section of ditto. 



5. Ditto, vertical section of thallus, showing apothecia. 



6. Ditto, thecse, containing protoplasm or spores in different 

 stages of development. 



