12 THE DETERMIXATIOX OF LICHEXS i:S' THE FIELD 



C. ThALLUS CKUSTACEOUS, GRAXULAE, or WA]VTI]S^G («). 



1. Th. often gelatinous and dark. Algse blue- 



green, Mjxophyceae (b) D. 



Th. not gelatinous. Algai belonging to 

 Chlorophycece, usu. green, but sometimes 

 reddish ( Trentepohlia) 2. 



2. Plants without apothecia or peritheeia (c) ... J. 

 Plants with apothecia or 2:»erithecia 8. 



3. Ap. or peritheeia immersed in pits formed 



in the rocky substratum (usu. calcareous 



rock) E. 



Thecia not in pits of the rock 4. 



4. Th. usu. yellow to purplish, or ap. yellowish 



to purplish, with polarilocular spores {d)... 6. 



Plant without these characters 5. 



5. Thecia often stalked, iclosed. Asci dissolv- 



ing so that the spores are loose and form a 



powdery mass F. 



Asci not dissolving. Spores not forming a 



powdery mass 7. 



6. Ap. with thalline margin Callopisma. 



Ap. without thalline margin Callopisma (Blastenia). 



7. Thecia borne on podetia (sometimes very 



short) 31. 



Thecia not borne on podetia 8. 



8. Thecia elongated, or linear, or radiate, or 



irregularly roundish (sometimes simulating 



peritheeia or lecideoid (<?) ap.) ; disc ±open. G. 



Thecia (peritheeia) closed or opening by a 



minute pore (ostiole) H. 



Thecia (apothecia) circular with ±plane 



(when young) and open disc 9. 



9. Fertile warts (verrucae) present, 1-many ap. 



in each wart. Sp. large (50 yu or more), 

 colourless or nearly so. Algal cells green... 10. 



Ap. not in fertile warts. Sp. seldom over 



30 ;i long 11. 



10. Sp. simple, large (usu. over 100 yu long), 1-8 



in ascus Pertusaria. 



Sp. 1-septate, very large (about 300 X 100 /i), 



1 in ascus Varicellaria. 



11. Ap. with two margins, an outer thalline one 



surrounding an inner proper one 28. 



Ap. with only one margin or without a margin . 12. 



12. Ascus containing many spores. Sp. simple, 



colourless, usu. minute 13. 



Ascus containing 8 or fewer spores (/"). 



Sp. various 10. 



13. Ap. with thalline margin 14. 



Ap. without thalline margin 15. 



