or ARTS AND SCIENCES. 199 



23. Sphj^rophoron. Apothecia terminal, spherical ; nucleus black, 

 dehiscent. 



Tribe II. ENDOCARPACEiE, Fr. —Apothecia immersed in the 

 thallus, globose, the thalline exciple attenuated into a neck, and 

 terminated by a discrete heterogeneous papillajform ostiole. 

 Nucleus deliquescent. Thallus horizontal, foliaceous or crus- 

 taceous. 



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



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



26. Pertusaria. Apothecia verruciform, with one or more blackish, 



papillate ostioles. 



Tribe III. VERRUCARIACEiE, Fr. — Apothecia rounded, a 

 closed proper exciple (periihecium) becoming pertuse with an 

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

 liquescent. Thallus crustaceous. 



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



28. Verrucaria. Perithecia closed, with a papillBeform or simply per- 

 tuse ostiole. 



Tribe IV. LIMBORIACEiE, Fr. — Apothecia rounded, the carbo- 

 naceous proper exciple closed, at length variously dehiscent. 

 Nucleus subceraceous, rigescent. Thallus crustaceous. 



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

 cent nucleus. 



I. USNEA, Dill., Hoffm. 



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

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

 lus cartilagineous,at first erect, sufl^ruliculose, 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 Stales. U. Jiomalea, 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, Rarnalina ho7nalea, Ach. Lich. p. 598, 

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

 detected elsewhere. 



