May, 1906.] Key to Liverworts. 533 



Perianth rough with tubercles or scales or smooth; leaves not 

 marked by moniliform cells; lower lobe helmet-shaped, some- 

 times expanded, ovate-lanceolate. 4. 



2. Leaves orbicular. 3. 



Leaves oblong from a narrowed base; lower lobe oblong-galeate. 



fragilifolia Tayl. 



3. Pinnate; lower lobe near stem, oblong-clavate ; underleaves ob- 



long, 2-cleft, flat. Asagravana Mont. 



Bipinnate; lower lobe distant from stem, oval or oblong; under- 

 leaves quadrate-ovate or obovate, emarginate, margin revo- 

 lute. Tamarisci Nees. 



4. Lower leaf lobe about % the size of the upper. Oakcsiana Aust. 

 Lower leaf lobe much smaller than the upper. 5. 



5. Underleaves scarcely wider than the stem, bifid, divisions entire, 



acute. 6. 

 Underleaves 2-3 times wider than the stem, bitid, divisions entire 

 or toothed, acute or blunt. 7. 



6. Perianth pyriform, slightly compressed, repand, smooth, obscurely 



carinate beneath and gibbous toward the apex. 



Eboracensis Lehm. 



Perianth broadly oblong, bowl-shaped with very short mouth, 



papillose, abruptly broad-carinate beneath, 1-many-nerved 



each side of the keel, 2— angled. saxicola Aust. 



7. Leaves lax, rather distant, lower lobes mostly expanded, ovate- 



lanceolate. Sporogonium unknown. aeoloUs Nees. 



Leaves crowded or close-imbricate, lower lobe seldom expanded. 

 Sporogonium known. 8. 



8. Perianth tuberculate. 9. 

 Perianth smooth. 10. 



9. Irregularly branching; leaves ovate, lower lobe sometimes expand- 



ed into a lanceolate lamina; underleaves not toothed; perianth 

 compressed pyriform, 2-4 carinate dorsally, 4-carinate ven- 

 trally. - Virginica Lehm. 



Pinnately branching; leaves round, lower lobe not expanded; un- 

 derleaves toothed; perianth obovate, retuse. dilatata Nees. 

 10. Underleaves cordate or rounded, sinuate-subdentate; perianth 

 convex dorsally, strongly keeled ventrally. sqitarrosa Nees. 

 Underleaves rather large, rounded; perianth sulcate dorsally, 

 acutely keeled ventrally. plana SuUiv. 

 Geocalyx Nees. 



Stem creeping with numerous rootlets; leaves ovate-quadrate, 

 bidentate, light to bluish green; underleaves cleft to the 

 middle, with linear-lanceolate divisions. graveolens Nees. 



Grimaldia Raddi. 



Thallus pale green, purple on the margin and below, with usually 

 distinct Avhitish pores, the scales beneath often extending far 

 beyond the margin and becoming whitish; peduncle barbed 

 whitish and chaffy at base and apex. harbifrons Bisch. 



Tliallus bluish-green with membranous margins, purple below; 

 ]ieduncle sparingly scaly at base, barbulate at the apex. 



riipcstris Lindenb. 

 (Jyniiioim'triimi Corda. 



vStem simple or imbricately branching, thickened at the apex ; 

 leaves ovate, bifid, wi{h a narrow scarious margin, bluisli- 

 green or brownish- or reddish-j-ellow to silvery-olive; no un- 

 derleaves. concinnatitm Corda. 

 Harpanthns Nees. 



Stem filiform, decumbent, usually simple, leaves roundish ovate, 

 their lobes acute; underleaves large, nearly 3-sided-lanceolate, 

 mostly entire; perianth splitting above on one side. 



scutatus Spruce. 



