186 BULLETIN OP 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. panperculus, 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. rufulns, 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,^ 87. 



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



Leaf margin serrulate. 



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



Leaf cells distinct (12-15 X 18-24//) . . . F. adiantoides,* 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. falcatulns, 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.)^ Plants aquatic, filiform, floating. 



Plants large, much branched, pedicel shorter than the 



capsule F. Julianas, 89. 



Plants small, little branched, pedicel longer than the 



capsule F. Hallianus, 90. 



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



^ See Appendix, no. 96. 



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



* See Appendix, no. 97. 



• Conomitrium of Manual. 



