50 Illinois State Laboratory of Natural History. 



i Midrib wanting or not apparent C 

 Midrib clearly apparent D 



f Sporogonium dorsal; elaters bispiral, free. II. PELLIA. 



r< j Sporogonium borne on under side of thallus near the 

 margin; elaters unispiral, adherent to the apex of 

 the valves. I. ANEURA. 



f Inner involucre tubular, at first terminal, at length 

 j) j dorsal; thallus sinuate or lobed. IV. STEETZIA. 



^ Inner involucre wanting or early vanishing E 



K 



Outer involucre wanting; fructification apical; thallus 

 simple or bifid. III. BLASIA. 



Outer involucre monophyllous, ventricose; Sporogonium 

 arising from lower surface of midrib; thallus fur- 

 cate. V. METZGKERIA. 



f Leaves incubous : i. e. the apex lying on the base of the 



next one above . . . GT 



F-J 



Leaves succubous: i. e. the apex lying under the base of 



the next one above 



{Leaves bilobed or with a small ventral lobe at base . . H 

 Leaves without ventral lobe at base, mostly 3-5-toothed, 

 lobed or parted L 



f Amphigastria present* I 



\ Amphigastria wanting; lower lobe usually convex un- 

 derneath. XL RADULA. 



. f Amphigastria entire or 2-toothed K 



j Amphigastria 4-5-lobed; lobes of leaves divided. XIII. 

 BLEPHAROZIA. 



* Arnphigftstria arc obsolete or wanting in three species of Lejeunia- 



