KEY TO THE GENERA. 31 
Struthiopteris. Sori round; indusium obscure, somewhat semicircular; 
fertile and sterile fronds unlike, fertile fronds pinnate; veins free. 
Onoclea. Sori round, soon confluent; indusium thin and hood-like; fertile 
and sterile fronds unlike, fertile frond twice pinnate; veins reticulated. 
(Page 107, Plate XL.) 
Woodsia. Sori roundish; indusium attached under the sori, more or less 
cut at the margin; veins free. (Page 111, plate XLII.) 
EE Sor? roundish or transversely elongated, at the ends of the veins, with 
an indusium attached at the base, and opening toward the margin. 
DAVALLIEA. 
Dicksonia. Sori very small, marginal, with a somewhat two-valved, cup- 
shaped indusium; veins free. (Page 117, Plate XLV.) 
B. Sporangia on a prolongation of the fertile vein, projecting 
beyond the margin of the frond, and surrounded by a cup-shaped 
MEE st ce ss + oo fe) EL YMENOPHYELACEZ:, 
Trichomanes, Sori marginal, within a cup-shaped indusium; the columella 
exserted and bristle-like; veins forked. (Page 121, Plate XLVII.) 
C. Sporangia ovoid or pear-shaped, sessile or shortly stalked, 
with a complete circular ring forming an apical, cap-like zone, open- 
igo by a longitudinal slit... . . . =. . . . SCHIZHACEA. 
Sechizzea. Sporangia naked, fixed in a double row on the fertile segments; 
sterile fronds, rigid, simple, or branched. 
Lygodium. Sporangia with a special scale-like indusium for each sporange, 
borne in a double row on the narrow spicate fertile segments; fronds 
leafy, climbing. (Page 127, Plate XLIX.) 
D. Sporangia naked, globose, clustered on the margin of a 
transformed frond, with an obscure ring, reticulated and pellucid, 
opening by two regular valves. . . . «© . « « OSMUNDACE. 
Osmunda. Sporangia pedicillate in branching spikes upon the margins of 
the very narrow segments; veins free. (Page 131, Plate LI.) 
E. Sporangia sessile, coriaceous, opaque, on the margin of a 
contracted frond, without reticulations or a ring, opening by a trans- 
verse slit into two valves; fronds not rolled up in the bud. 
OPHIOGLOSSACE. 
Botrychium. Sporangia arranged on one side of a pinnate rachis; veins 
free, forked. (Page 139, Plate LV.) 
Ophioglossum. Sporangia cohering on a 1-celled 2-ranked simple spike ; 
veins reticulated. (Page 147, Plate LVIX.) 
