186 BULLETIN OF THE UNIVERSITY OF WISCONSIN. 



Marginal leaf -cells papillose. 

 Costa percurrent . . . . . . F. Ravenelii, 85, 



Costa ceasing below apex . . F. Garberi, 86. 



Leaves without a border. 



Acute, cells densely chlorophyllose, obscurely papillose F. Donnellii, 85. 



Acute, almost hyaline, smooth F. pauperculus, 99. 



Obtuse, cells pellucid, operculum conic . . F. obtusifolius, 86. 



Apiculate, operculum with acicular beak . F. osmundoides, 87. 

 Leaves with a thick reddish border. Plants submersed, 



rigid F. rufulus, 84. * 



B. fruit lateral. 



i. Leaves without a border. 



Obtuse, entire, plants 2-5 cm. high, fruit sub-terminal F. polypodioides, 88. 

 Rounded at apex, irregularly serrate, 1-2 cm. high, fruit 



sub-basal F. sub-basilaris, 88. 



Mucronate, regularly serrulate, fruit basal or sub-basal F. taxifolius, 8 87. 



2. Leaves bordered by several rows of paler, often incrassate, cells. 



Leaf margin serrulate. 



Leaf cells obscure (6-9 X 6-12/0 . . F. cristatus, Wils., 8 87. 



Leaf cells distinct (12-15 X 18-24/0 . . . F. adiantoides, 4 88. 

 Leaves entire or slightly denticulate at the apex. 



Inferior lamina bordered, ceasing abruptly at base F. Floridanus, 83. 



Inferior lamina not bordered, tapering below . F. falcatulus, 98. 



II. (PACHYFISSIDENS.) Leaves rigid, composed of more than 

 one layer of cells, opaque. 



Plants growing in water or very wet places . . F. gradifrons, 89. 



III. (OCTODICERAS.) 6 Plants aquatic, filiform, floating. 



Plants large, much branched, pedicel shorter than the 



capsule F. Jnlianns, 89. 



Plants small, little branched, pedicel longer than the 



capsule . F. Hallianus, 90. 



1 F. ventricosus of L. & J. Man. 



2 See Appendix, no. 96. 



*F. decipiens De Not., L. & J. Man. 

 4 See Appendix, no. 97. 

 ' Conomitrium of Manual. 



