AND BRITISH AMERICA. 13 



p. 163 ? Jfonterey ! Appears to me to differ from R. scopulorum in its 

 softish, plane, often deeply lacunose, and thin thallus, as well as in the 

 apothecia. — Roccella, a genus nearly allied to the present and the 

 last, and diffused throughout the warmer regions of the globe, has not 

 as yet any North American representative. I saw, however, in a small 

 collection of " Algse from Carolina, Bermudas, and the Caribbees, by 

 the Rev. Mr. Clerk," in the British Museum, a Roccella, which resem- 

 bled R. phycopsis, Ach. ; but it is uncertain at which of the above lo- 

 calities this Lichen was obtained. 



1. R. calicaris, Fr. Thallus ramose-foliaceous, cartilagineous, ri- 

 gescent, lacunose, glaucous ; apothecia pedicellate, with elevated mar- 

 gins, disk plane, palish. Fr. Lichenogr. p. 30. — a. fraxinea, Fr. ; 

 lacinise longer and broader, the fertile ones plane ; apoth. lateral. R. 

 fraxinea, Ach. — /?. fasligiata, Fr. ; laciniae shorter, fastigiate, sub- 

 compressed, lacunose ; apoth. somewhat terminal. JJ. fasligiata, Ach. 

 — ;'. canaliculata,Fi. ; lacinis sublinear, narrow-attenuate, fertile ones 

 channelled ; apoth. afRsed to the reflexed apices. Lichen calicaris, 

 L. R. fasligiata, §., Ach. — S. farinacea, Schser. ; laciniae linear- 

 attenuate, sublacunose (sorediiferous), rigid; apoth. scattered. R. far- 

 inacea, Ach. 



Very common : «, /?, and y, on trees, rails, &c. ; the last especially 

 in mountain forests ; d, abundant in the New England mountains, and 

 northward, on trees and rocks. New York, Torrey. Pennsylvania, 

 Muhl. 



2. R. polymorpha, Ach. Th. caespitose, cartilagineous-rigid, lon- 

 gitudinally costate-rugose, glaucous (and pallescent), often sorediifer- 

 ous and the soredia capituliform ; apoth. subterminal, pedicellate, with 

 elevated margins, disk concave, pale. Fr. Lichenogr. p. 32. — (S. tinc- 

 toria, Ach. ; lacinice sublinear, diffuse, linear-lacunose, lacerate-incised 

 and pulverulent at the apices. Ach. Lichenogr. p. 601. 



Rocks and stones, fertile ; New England, and westward, very com- 

 mon. New York, Halsey. Pennsylvania, Muhl. Arctic America, Rich. 



IV. CETRARIA, Ach., Fr. 



Apothecia scutellate-peltate, affixed obliquely to the apices of the 

 thallus. Thallus cartilagineous-membranaceous, originally ascendant ; 

 smoothish on the under side ; lobes either somewhat terete, or foliaceous 

 and somewhat concave above. 



