AND BRITISH AUERICA. 7 



24. Endocakpon. Apothecia pale, included in the foliaceous thallus. 



25. Sagedia. Apothecia blackish, immersed in the crustaceous thallus. 



26. Pektusaria. Apothecia verrucaeform, with one or more blackish, 



papillate ostioles. 



Tribe III. VERRUCARIACE.E, Fr. — Apothecia rounded, a 

 closed proper exciple (perithecium) becoming pertuse with an 

 ostiole, or at length open. Nucleus gelatinous, subhyaline, de- 

 liquescent. Thallus crustaceous. 



27. CoNOTREMA. Perithecia at length open ; nucleus subdisciform. 



28. Verrfcaria. Perithecia closed, with a papillseform or simply per- 

 tuse ostiole. 



Tribe IV. LIMBORIACE^E, Fr. — Apothecia rounded, the carbo- 

 naceous proper exciple closed, at length variously dehiscent. 

 Nucleus subceraceous, rigescent. Thallus crustaceous. 



29. Ptrenothea. Perithecia at length pertuse, protruding the fatis- 

 cent nucleus. 



Div. I. GYMNOCARPI, Schrad., Fr. 



Tribe I. PARMELIACE^, Fr. 



I. USNEA, Dili., Hoffm. 



Apothecia rounded, peltate, subterminal ; disk open, placed upon the 

 filamentous medullary stratum, the margin mostly radiate-ciliate. Thal- 

 lus cartilagineous, at first erect, sufliruliculose, becoming with age more 

 or less filamentous or pendulous, the crustaceous cortical stratum some- 

 what separate from the medullary. 



A genus universally diffused; and the first species occurring, in 

 one or other of its forms, in every quarter of the globe. This spe- 

 cies extends throughout the United States. U. homalea, Tuckerm. 

 Enum. 1845, with a softish, much compressed, ancipital, rugulose, fas- 

 tigiate and attenuate-branched thallus, and plane apothecia, with scarce- 

 ly elevated, obtuse margins, Ramalina homalea, Ach. Lich. p. 598, 

 was discovered on the coast of California by Menzies ! but has not been 

 detected elsewhere. 



