4 THE DETEKMIXATIOX OF LICHEiNS IN THE FIELD 



Til. seldom distinctly stellate or radiate- 

 orbicular. Sp. simple and colourless 22. 



22. Under surface of th. usu. with rliizime. Ap. 



and spermogones on upper surface of th.... Parmelia (/). 

 Under surface of th. without rhizinse. Ap. 



and sp3rmogones on margin of th Platysma (k). 



23. Th. ± orbicular, appressed to substratum, with 



radiating lobes at the circvmiference 24. 



Th. not having radiating and appressed hjbes 36. 



24. Algal cells blue-green (A'oi^oe or i?/r?//rrj7V^). 25. 

 Algal cells green 26. 



2-5. Ma]-gins of pale th. and reddi.sh ap. silvery- 

 white Pannaria rubiginosa. 



Th. brown or dark. Very rare plants. Algal 



cells Ovular? a Pterygium . 



26. Th. yellow, jnirple with K. Ap. yellow or 



reddish, purple with K. S]).8, polai-ilocular. 27. 



Th. yellow, K — , not corticate nor rhi^-inose 



beneath (/). Ap. yellowish, K — . On rocks. 28. 

 Th. usu. greyish or whitish (if yellowish, 



corticate and rhizinose beneath). Ap. 



not yellow 29, 



27. Th. with cortex and rhizinai beneath (/)... Xanthoria parietina. 

 Th. not corticate (except in P. elegans), 



nor riiizinose beneath Placodium (m). 



28. Sp. 8, simple or polarilocular { = CandeJa- 



riella m. of the Monograph) Placodium medians. 



S]!. many in ascus, simple Candelariella crenata. 



29. TIk with cortex and rhizinai beneath. Ap. 



with thalline margin 21 («)• 



Th. without cortex and rhizinse beneath. Ap. 



with or without th. margin 30. 



30. Th. leprose K — , white or yellowish- white . . . Crocynia lanuginosa. 

 Th. not lop-ose, minutely radiate at circum- 

 ference 31. 



Th. not leprose, distinctly radiate at circum- 

 ference 33, 



31. Ap. black 32. 



Ap. reddish K-f pur2:)le. Sp. polarilocular. 



Th. greyish K— []\ teicholjffnm ( = P. 

 erytlirocnypu m ) & P. lalla rei.'] Placodium. 



32. Th. greyish K -f purple. Sp. polarilocular. 



Pyrenodesmia chalybaea. 

 Th. whitish K — . Sp. simple... Lecanora (dalactina group). 

 Th. white K — . Sp. nmriform Rliizocarpon (8 c^ 14). 



33. Th. white or almost so. Ap. dai-k. Sp. 



1-septate 34. 



Th. greyish or brownish. Ap. dark or 



coloured. Sp. simple and colourless 3.3. 



34. Th. K — . Ap. with a thalline margin. Sp. 



colourless Placolecania candicans. 



