22 THE DETEimiXATIOX OF LICHEXS IX THE FIELD 



I. TlIALLL'S CliUSTACEOrS, GRAXULAE, OR T^-AXTIXG. APOTHECIUM 

 AVITHOUT THALLIXE ZVEARGIX (a). ASCUS 8-SPORED. 



1. Algal cells reddish or 3'ellow (Trentejjohlia). 



Sp. septate, colourless 2. 



Algal cells green. Sp. various 1. 



2. Ap. dark, often somewhat irregularl}'- roundish 3. 

 Ap. brightly coloured, cup-shaped, the proper 



margin well-developed and usu. paler Gyalecta. 



3. Ap. with a proper margin, often pruinose ... Lecanactis. 

 Ap. without a proper margin (a pseudo- 



thalline margin is sometimes jn'esent), not 



pruinose Platygrapha (b). 



4. Sp. colourless and simple Lecidea (c). 



Sp. colourless (or nearly so) and septate 5. 



Sp. brown or dark, septate 7. 



5. Aseus containing 8 (sometimes fewer) spores. 6. 

 Ascus containing only 1 large spore, occa- 

 sionally somewhat brownish S. 



<j. Sp. 1-septate, ellipsoid, usu. less tlian ?> times 



as long as broad Biatorina (</, e). 



Sp. 3- or more-septate, fusiform, usu. about 



4 times as long as broad Biiimbia (<9). 



Sp. 3-man3'-septate, acicular, usu.;more than 



10 times as long as broad Bacidia. 



Sp. muriform, oblong, often large and usu. 



about twice as long as broad Rhizocarpon (/*). 



7. Sp. muriform, oblong, often large and usu. 



about twice as long as broad Rhizocai'pon (/'). 



Sp. 1-septate, about twice as long as broad. 



Seldom parasitic Buellia ((/). 



Sp. 3-septate, about three times as long as 



broad. Parasitic on other lichens or on 



liverworts Leciographa. 



8. Sp. 7-10-septate, very large (usu. over 100 /.c 



long). On trees or rocks Bombyliospora. 



Sp. muriform, large (usu. less than 100 /x 

 long). On mosses Lopadium. 



(a) Some plants belonging to Graphidinese, but having roundish 

 ap., may be confused Avith this group. Some plants belonging to 

 Lecanora, Aspicilia, Jonaspis, Hinoih'na, and Lecania have the 

 thalline margin of the ap. evanescent or little evident, and so may be 

 confused with plants of this group, in which there are no algal cells 

 beneath the ap. and the hypothecium is frequently dark. 



{h) Some other plants belonging to Graphidinea? (e.g., Artlionia 

 lurida) may be found here. (See Sectional Key G.) 



(c) Including Lecidea dicksonii, which is often placed under 

 Aspicilia. Some Aspicilias and Lecanoras may be found here. In 

 Aspicilia the ap. are innate ; in Lecanora gonidia are present beneath 

 the ap. Sceomyces rufus (when the apothecia are sessile) may be 

 found here. 



