THE J)ETEKM1NATI()N OF 1,1('IIK.NS I.N THE EIEI/D IT) 



((0 Only a few plants are (leterniinal)lu in tliis case.. 



{d ) Also includes forms of Placodium I oh ul a tit in and P. miuia- 

 fnluin in which the th. is scarcely radiatel3'-squamulose at the 

 margin. 



In Callo2)isma (including Blastenia) there is a certain amount of 

 variation in the colour and reaction of the th. and ap., and occa- 

 sionally^ the spores do not appear to be polarilocular (C. nivale, 

 O. luteo-alhum^ C. cerinellnm, and C. ruj^cstre). Jn C. ei^ixanthum 

 (sometimes placed under Candelariella) the reaction with potash is 

 negative both for the th. and ap. The ascus usu. contains S 

 spores, but 16 may be present in G. ccrineUiim. The sj)ores ina^^ 

 be + polarilocular in Candelariella vitelUna, the ascus of which 

 usu. contains 16 or more spores. 



(<'^) A lecideoid ap. has no thalline margin and is without algal 

 cells at its base. 



(/") Lecanora sa/nhnci is an exception. It has 12-82 spores in 

 the ascus. 



(y) Karely the th. is greyish and the ap. darker. 



(70 Table I does not include plants given in ])revious parts of the 

 key, e. g., Opegrapha is given in Table Gr, and Blatorella is included 

 with the man^'-spored lichens. 



(/) In Lecania the spores are often simple in part, and may thus 

 be confused with Lecanora, which usu. has relatively shorter spores 

 (about twice as long as broad). The septum is often only apparent 

 after treatment with K. 



D. Thallus gean^ular or crustaceous (oftex gelatinous) 



W^ITH BLUE-GREEN ALGAL CELLS, MyXOL^UYCE^I: («). 



1. Th. ^gelatinous when moist, corticate or not. 



Algal cells usu. scattered throughout 



the th 3. 



Th. not (or slightly) gelatinous when moist, 

 corticate. Algal cells in a definite laj^er 

 under the cortex 2. 



2. Ap. with a thalline mai-gin Paimaria. 



Ap. without a thalline margin Parmeliella (Pannariella). 



3. Algal cells Xostoc or Scytonema 4. 



Algal cells liivularia, Gloeocapsa, or Chroo- 



coccus 9. 



4. Algal cells iV^(96-^oc 5. 



Algal cells Sci/fonema (b) 8. 



5. Th. with a cellular cortex (c) 6. 



Cortex not cellular 7. 



6. 8p. simple. Ap. with a proper margin Lemmopsis. 



Sp. septate and mui-iform. Ap. witli a thai- 

 line margin Leptogiiim. 



7. Sp. simple Physma (Lempholemma) . 



Sp. septate-muriform CoUema (d) . 



8. Th. not corticate. Ap. with thalline margin. 



Sp. simple Porocyplius. 



Th. corticate, often minutely coralloid. Ap. 



without thalline margin. Sp. septate Placynthium (<"). 



