Xll 



DESCRIPTION OF THE PLATES. 



5. Ditto, Ndx.fastigiata. 



6. Ditto, var. calicaris. 



7. R. scopulorum. 



8. R. farinacea. 



9. Ditto, portion of thalline filament magnified, showing the 

 soredia. 



PLATE VII. 



1. Physcia jprunastri. 



2. P. furfuracea. — a. Upper surface, b. Under surface. 



3. P. ciliaris. 



4. Ditto, under surface of thalline lacinise. 



5. Ditto, vertical section of thallus showing a spermogone. 



6. Ditto, vertical section of a spermogone, showing the sterig- 

 mata and spermatia. 



7. Ditto, vertical section of mature apothecium. 



8. Ditto, vertical section of young apothecia. 



9. Ditto, progressive development of the spore. 



10. Ditto, segment of an old spore. 



PLATE VIII. 



1. Cetraria Islandica, large variety. 



2. Ditto, common form. 



3. Ditto, apothecium magnified* 



4. Ditto, section of ditto. 



5. Ditto, marginal cilia of thallus bearing the spermogones on 

 their apices. 



