THE DETERMINATION OF LICHENS IN THE FIELD 23 



(d) Tlie septum is often thin, so that the spore appears to be 

 simple — in fact, some of the spores are really simple. There are 

 sometimes more than 1 septum present (1-3) in B. cyrtrlla and 

 B. episema. 



(e) Species of Lecania with leeideoid ap. ma}' be found here. 



(/) The longitudinal or oblique septa are sometimes indistinctly 

 sho%vn, especially in young spores. 



(y) Species of Binodina with leeideoid ap. may be found here. 



J. Plants with ttiallus crustaceous, granular, or avanting, 



WITHOUT APOTHECIA OR PERTTHECIA («). 



1. Th. usu. dark, ibgelatinous. Algal cells 



blue-green (MyxophyccLe) Tables D & H. 



Th. of 4ispherical greenish mucilaginous 

 granules aggregated together. Algal cells 

 + ellipsoidal {Coccomyjca), forming a cen- 

 tral mass surrounded by fungal filaments. 

 Usu. on ground * Botrydiiia. 



Th. not gelatinous, seldom dark. Algal cells 



green or reddish (Chlorophj'cese) 12. 



2. Th. with roundish soredia or wath minute 



+ cylindrical projections (isidia) 3. 



Th. forming white powdery patches, 1-J^ 

 inches (or more) in diameter, K-f yellow 



then red, C— I — . On trunks of trees ... Phlyctis. 



Th. with whitish soredia tasting of quinine . Pertiisaria amara. 



Th. without such characters 7. 



3. Medulla of th. becoming blue with I A. 



Medulla of th. not becoming blue with I ... 5. 



4. Medulla 1+ dark blue. Th. white-sorediate, 



K — C - . On trees (rarely rocks) Pertusaria multipuncta. 

 Medulla I -f pale blue. Th. whitish, papillose, 



K-f 3^ellow then ferruginous-red C — . On 



rocks Pertusaria dealbata. 



Medulla 1+ blue. Th. greyish, sorediate,K — 



C—, with black hypothallus. On rocks... Lecidea sorediza. 



5. On trees or rocks (if on ground or mosses 



C — ) .' Pertusaria. 



On ground, encrusting mosses and other 

 vegetation ; soredia or th. having a reddish 

 coloration with C. Alpine plants 6. 



6. Th. gre^'ish, elf use, papillose, K+ yellowish. Lecidea arctica. 

 Th. greyish, subeffuse, papillose, at length 



soredia te, K -f- yellowish-red Lecanora geminipara . 



Th. white, effuse, K-f yellowish, white- 

 sorediate Pertusaria bryontha. 



7. Th. yellow (sometimes pale or greenish) or 



reddish 8. 



Th. wdiite, grey, brown, or dark (seldom 

 greenish) 23. 



