xviii 



DESCRIPTION OF THE PLATES. 



1 8 . L. atra, section of thallus, showing apothecia, and sper- 

 mogones, b. 



19. Ditto, apothecium, magnified. 



20. Ditto, spores, young and mature. 



21. L. varia, ditto. 



PLATE XIV. 



1. Lecidea aeruginosa. 



2. Ditto, theca and spores. 



3. Ditto, free spore. 



4. Lecidea atro-alba, var. concentrica (Leight.). 



5. L. geographica. 



6. Ditto, portion of thalhis, magnified, showing dendritiform, 

 black, marginal hypothallus, a. 



7. Ditto, apothecium magnified. 



8. Ditto, section of ditto. 



9. Ditto, spore. 



10. Lecidea femtginea. 



11. Ditto, apothecia, young and old, magnified. 



12. Ditto, section of young and old apothecia, showing the 

 concave and convex conditions. 



13. Ditto, spore. 



14. Ditto, spore acted on by iodine. 



15. L. sanguinaria. 



16. Ditto, section of apothecium, showing the blood-red sub- 

 stratum. 



