20 THE DETER^IIXATIO?^- OF LTCITEXS I;N^ THE FIELD 



3. Horizontal th. wanting. Perithecia yellowish 



and surrounded by a yellowish-green go- 

 nidial sheath. Ascus with many minute 



sp- ••• Thelocarpon. 



Perithecia brown or black, usu. scattered on 

 a horizontal th. {d). Ascus with 1-8 

 spores 4. 



4. Paraphyses disappearing. Algal cells present 



in hymenium. Sp. muriform Staurothele. 



Paraphyses disappearing. Algal cells not 



jDresent in hymenium, Sp. various 5. 



Paraphyses persistent. Algal cells not 



present in hymenium. Sp. various 7. 



5. Sp. simple, colourless (rarely brownish), 8 in 



' ascus. Ostiolar filaments usu. present ... 6. 



Sp. 1-3-septate, colourless (rarely brownish), 



8 in ascus. Ostiolar filaments usu. absent. Thelidium. 



Sp. muriform, colourless or brown, 1-8 in 

 ascus. Ostiolar filaments sometimes dis- 

 tinct Polyblastia. 



6. Sp. cylindrical with clavate ends, 30-40 X 



3-4/A Sarcopyrenia. 



Sp. ellipsoid or subglobose Verrucaria. 



7. Sp. simple, colourless or brownish, 2-3 times 



as long as broad Thrombium. 



Sp. man3^-septate, colourless, acicular, about 



30 times as long as broad Gongylia. 



Sp. muriform, colourless or brownish, 2-5 



times as long as broad Microglaena. 



8. Perithecia often coherent. Sp. muriform, 



50-110 X 20-40 yu. On hazel Anthracothecium. 



Perithecia scattered. Sp. 1-many-septate, 



usu. much smaller 9. 



9. Paraphyses bi-anched or entangled, or indis- 



tinct or wanting 10. 



Paraphyses unbranched and distinct (<?) 12. 



10. Asci cylindrical, elongate, narrow with 1- 



septate colourless spores arranged vei-ti- 



cally or obliquely Acrocordia. 



Asci clavate or ovate. Sp. + massed, colour- 

 less or brown, 1 -many-septate 11. 



11. Sp. colourless. 1-5-septate, 2-5 times as long 



as broad (/) Arthopyrenia. 



Sp. colourless, 1-many-septate, 7-10 times 



as long as broad. On bark of trees Leptorhaphis (y). 



Sp. brown, usu. 1 -septate (rarely 3-5-septate), 



2-3 times as long as broad Microtheiia. 



12. Sp. 8, brown, 3-septate, each cell with an oil- 



drop. Perithecia black. Th. with a iboily 



appearance, often yellowish Pyrenula. 



Sp. colourless. Ap. frequently coloured 13. 



