322 SYSTEMATIC 



Thallus with Palmella gonidia. 

 Apothecia single. 



Hypothecium dark-brown. 



Spores simple i. Lithographa Nyl. 



Hypothecium colourless or brownish. 

 Spores colourless. 



Spores simple 2. Xylographa Fries. 



Spores elongate 3-8-septate 3. *Aulaxina Fde. 



Spores brown. 



Spores i-septate 4. Encephalographa Massal. 



Spores pluri-septate, then muriform 5. *Xyloschistes Wain. 



Apothecia compound. 



Spores simple, colourless 6. Ptychographa Nyl. 



Spores pluri-septate, colourless 7. *DipIogramma Miill.-Arg. 



Thallus with TreiUepohlia gonidia. 

 Spores elongate i-multi-septate, the cells longer than wide. 

 Spores brown. 



Spores i-(rarely more)-septate 8. Melaspilea Nyl. 



Spores 3-septate (apothecia rudimentary) g. *Gymnographa Miill.-Arg. 



Spores colourless. 



Spores acicular, coiled (many in the ascus) 10. *Spirographa A. Zahlbr. 



Spores fusiform, straight 11. Opegrapha Humb. 



Spores muriform. 



Spores elongate, central cells finally muriform 12. *Dictyographa Miiil.-Arg. 

 Spores elongate, septate, cells wider than long. 

 Paraphyses unbranched, filiform. 



Spores multi-septate, colourless 13. Graphis Adans. 



Spores multi-septate, brown 14. Phaeographis Miill.-Arg. 



Spores muriform, colourless 15. Graphina Miill.-Arg. 



Spores muriform, brown 16. Phaeographina MiiU.-Arg. 



Paraphyses clavate, warted at tips 17. *Acanthothecium Wain. 



Paraphyses branched, interwoven above 18. *Helminthocarpon Fde. 



Thallus with Phycopeltis gonidia (epiphyllous). 



Spores elongate, 3-9-septate, colourless 19. *Opegraphella Miill.-Arg. 



Spores elongate, l-septate, brown 20. *Micrographa Miill.-Arg. 



XX. Chiodectonaceae 



Specially distinguished in this subseries by the grouping of the somewhat 

 rudimentary apothecia in pseudostromata in which they are almost wholly 

 immersed. In form they are roundish or linear; the spores are septate or 

 muriform. The thallus is thinly crustaceous and continuous : in Glyphis, 

 Sarcograpka and Sarcographina there is an amorphous upper cortex, the 

 other genera are non-corticate. Algal cells are Trentepohlia with the 

 exception of two epiphyllous genera associated with Phycopeltis. 



Genera and species are mostly tropical. Sclerophyton with five species 

 is represented in Europe by a single British specimen, 6'. circumscriptum. 



The form of the paraphyses is a distinguishing character of the genera. 



