i35 



4- Section of thallus. 



a, protecting layer ; b, algal layer; c, medullary layer. 



5. Paraphyses and spore-sac with spores. 



6. Spores. 



6. Lecidea Ach. Lich. Univ. 153. 1810. 



As already stated in the discussion of Biatora this group presents 

 the general characters of that genus. The following are some of 

 the differences : It is somewhat lower in the scale of development, as 

 is indicated by the more rudimentary thallus ; the hypothecium is 

 dark, though this is not a reliable distinguishing character, as already 

 indicated ; the thecium is also more or less brown to dark in color ; 

 the paraphyses are perhaps somewhat shorter and less distinct ; the 

 epithecium is quite constantly dark to black. In general, the tissue 

 of the apothecium is somewhat more brittle. 



The majority of the species occur upon rocks and tree trunks, a 

 few upon old fences. 



PLATE 19. 

 Lecidea melancheima Tuck. 



1. Plants natural size. 



2. A portion of above magnified. 



3. Section of apothecium. 



4. Section of thallus. 



5. Paraphyses and spore-sac with spores. 



6. Spores. 



7. Algae. 



7. Celidiopsis Mass. Flora, 15: 487. 1857. 



Further study of this genus is necessary to decide whether it 

 should be combined with Bilimbia or not. It is distinguished from 

 that genus by the dark hypothecium, a character which is by no 

 means constant, even less so than in Lecidea. In all other respects 

 it resembles Bilimbia, making, however, due allowance for varietal 

 differences. Only a few species occur in the territory. Their habitat 

 seems to be tree-trunks and moss. 



PLATE 15. Fig. 4. 

 Celidiopsis. 

 Spore-sac, spores and paraphyses. 



