TlIK DKIEUMIXATIOX OF LTCITENS TX TTTK FTEf.D 3 



9. Algal cells bright-green Sticta. 



Algal cells blue-green {Nosfoc) Stictina. 



10. Th. vividly bright-green when moist. L'su. 



on soil 11. 



Th. not vividly bright-green when moist ... 12. 



11. Aj). sunk in depressions of the th Solorina saccata. 



Ap. not sunk in depressions of the th Peltidea. 



12. Th. with large pits above, or saffron-coloured 



beneath, or with ap. sunk in pits 13. 



Th. smooth or little wrinkled above, not 



saffron beneath. Ap. superHcially ])laced . lo. 



13. Th. zhorbicular smooth, saffron beneath. A]). 



usu. in pits. Sp. 1-septate, brown. Al- 

 pine plant Solorina crocea. 



Th. widely spreading, pitted, not saffron 

 beneath. Ap. superTicial. Sp. 1-7 septate. 



colourless 14. 



1-1. Th. strongly reticulate-pitted. Algal cells 



green Lobaria pulmonaria. 



Th. with less evident and more irregular pits. 



Algal cells blue-green (JVosfoc) Lobarina scrobiculata. 



15. Th. with blue-green algal cells or in Bicasolia 



(which has green algal cells) with very 

 large lobes (often more than 2 cms. broad) 16. 



Th. with green algal cells ; lobes usu. less than 



1 cm. broad 20. 



16. Th. + orbicular-radiate, of shell-like lobes 



with radiating lines and with a bluish- 

 black fibrillose surface beneath ....*..... Parmeliella plumbea. 

 Th. not orbicular-radiate and not dark-blue 



beneath 17. 



17. Th. corticate and sometimes glabrous beneath. 18. 

 Th. without cortex beneath, but usu. with 



nerves and rhizinte 19. 



IS. Th. with blue-green algal cells {Nostoc) ; 

 under surface glabrous or nearly so exce])t 



in the very rare N. resupinatum Nephromium. 



Th. with green algal cells ; under surface 



+ covered with tomentum and rhizinse ... Ricasolia. 



19. Th. green when moist, with cephalodia (Ji) 



and green algal cells Peltidea. 



Th. grey, brown or dark when moist, without 

 cei)halodia and with blue-green algal cells 

 {Xostoc) Peltigera. 



20. Th. yellow, becoming purple with K. Ap. 



small with colourless polarilocular spores. Xanthoria parietina. 

 Th. not yellow, or if so, not becoming 

 ])urple with K. Sp. simple and colourless or 

 1-septate and brown 21. 



21. Th. usu. distinctly stellate or radiate-orbicular. 



Sp. 1-septate and brown Physcia ( /) . 



h2 



