8 KEY TO THE ARRANGEMENT. 



somewhat crenulate margin ; a coloured (rarely black) 

 connivent proper exciple, which is now explanate, 

 received in, or veiled by an often evanescent, thalline 

 one. Spores ellipsoid, fusiform, or acicular, bi-quadri- 

 pltirilocular, or the cells rarely also irregularly, or 

 even murally divided ; uncoloured. Thallus uniform. 



36. UKCEOLARIA. Apothecia urceolate-scutella?forru; a 



black, counivent, proper exciple becoming oftener 

 explanate, and bordering the black disk with its more 

 or less whitened margin, which is finally discrete from 

 the lecanorine, thalline one (now obsolete). Spores 

 ovoid-ellipsoid, muriform-plurilocular, brown. Thal- 

 lus uniform. 



37. THELOTREMA. Apothecia urceolate, now verrucae- 



form, or endocarpeiue,but at length largely scutellate, 

 the disk veiled by an inner exciple (often obsolete); 

 proper exciple variously coloured, somewhat torn- 

 margined, concrete with the thalline. Spores ellip- 

 soid and oblong, bi-plurilocular, or finally rauriform- 

 multilocular, brown, or decolorate. Thallus crusta- 

 ceous, uniform. 



38. GYROSTOMUM. Apothecia from urceolate finally ex- 



plauate, orbicular or often elongated-difforrn ; a black 

 proper exciple, with entire margin, clothed at first by 

 an evanescent thalline one. Spores ellipsoid, muri- 

 form-plurilocular, brown. Thallus uniform. 

 * MYRIANGITJM. Apothecia lecanoroid, multilocular, 

 each loculament developing a single theke, unaccom- 

 panied by paraphyses. Spores oblong-ovoid sub- 

 muriform-multilocular, colourless. Thallus rounded, 

 more or less plaited or lobulate at the circumference, 

 blackish-brown ; without gouidia. 



Trib, 2. LECIDEACEI, Apothecia rounded, margined (nor- 

 mally) only by the proper exciple (patellaiform). 



