DESCRIPTION OF THE PLATES. 



XV 



, 10. U. potymorpha, portion of margin of the thallus, showing 

 the cilia or fibrils. 



11. Ditto, apothecia, in different stages of development: a, 

 young and papillate ; b, mature and gyrose-plicate. 



12. Ditto, section of an apothecium, and of thallus showing the 

 rhizinse. 



13. Ditto, portion of thallus of another variety, showing rela- 

 tive position of spermogones, a. 



14. Ditto, section of thallus, showing spermogones. 



15. Ditto, section of a spermogone. 



16. Ditto, spores of different varieties. 



17. TJ. erosa, spore. 



PLATE XI. 



1. Sticta pulmonaria. — a. Upper surface, showing apothecia 

 and lacinise. b. Lower surface, showing gibbi. 



2. Ditto, extremity of a thalline lobule, magnified, showing 

 spermogones, soredia, and apothecia, one of which, a, is habited 

 by the Celidium Stictarum, a parasitic species. 



3. Ditto, section of an apothecium, a; and of thallus showing 

 old and young spermogones, b. 



4. Ditto, spore. 



5. Ditto, spore germinating. 



6. Sticta scrobicidata, upper surface, showing the apothecia 

 and marginal soredia. 



7. Ditto, spore. 



