xxvi 



DESCRIPTION OF THE PLATES. 



7. Pertusaria communis, theca and spores acted on by iodine. 



8. Ditto, transverse section of a theca and spore, showing 

 their thickened walls. 



9. Ditto, transverse section of a spore, showing the different 

 coats of the epispore and endospore. 



10. Ditto, section of a spermogone. 



11. Ditto, sterigmata and spermatia. 



12. Sag edict aggregata. 



13. Ditto, thallns, magnified. 



14. Ditto, apothecial warts, more highly magnified. 



15. Ditto, section of thallns, showing apothecia with their 

 necked openings, a. 



16. Ditto, spore. 



17. 8. cinerea, spore. 



PLA.TE XXII. 



1. Verrucaria nitida. 



2. Ditto, portion of thallns, magnified. 



3. Ditto, ditto, still more highly magnified, showing relative 

 position of spermogones, h, to apothecia, a. 



4. Ditto, apothecinm, magnified. 



5. Ditto, section of ditto. 



6. Ditto, spores in different stages of development. 



7. Ditto, one of the contained cellnles of the spore. 



8. Ditto, spermatia. 



9. V. gemmata, section of apothecium. 



