561 
in a few cases the sporangia are in spikes or panicles: prothallium 
above ground, green, monoecious or divecious.—The following is an 
artificial key to the genera. 
* Sporangia surrounded by a vertical ring, bursting transversely, and collected in 
sori on the back or margin of a leafy frond. 
+ Sori naked. 
1. Polypodium. Sori round, dorsal: fronds pinnatifid. 
2. Gymnogramme. Sori dorsal, following the veins: fronds pentagonal (hispid in 
our species). 
3. Notholeena. Sori marginal: fronds variously divided, tomentose or covered 
with a waxy powder. 
++ Sori covered with an indusium. 
“4+ Sori marginal, covered with a reflexed portion of the frond which is more or less 
altered and membranous. 
= Sporangia borne on the reflexed portion. 
4. Adiantum. [fronds mostly smooth, with polished black stipes. 
== == Sporangia borne on a continuous vein-like receptacle which connects the 
apices of the veins. 
5. Pteris. Fronds large, coarse (in our species ternate and triangular). 
== == = Sporangia at or near the ends of unconnected veins borne on the under 
surface of the frond, 
6. Pella. Sori on the upper part of the veins, forming a cortinuous marginal 
band: fronds mostly smooth. 
7. Cheilanthes. Sori minute at the ends of the veins: indusium interrupted or, 
if continuous, the ultimate segments bead-like: fronds mostly chaffy or woolly. 
++ ++ Sori dorsal, provided with special indusia. 
= Indusia linear or oblong, attached along a vein, 
8. Asplenium. Sori oblique to the midribs of the pinnie. 
9. Woodwardia. Sori parallel to the midribs of the pinna, 
10. Dryopteris. Indusia superior, orbicular and fixed by the center, or round-reni- 
form and attached by the sinus. 
11. Woodsia. Indusia inferior, bursting above the sorus into stellate lobes which 
are more or less concealed by the ripened sporangia. 
* * Sporangia pear-shaped, surrounded by an apical ring, bursting longitudinally, 
and borne in panicles. 
_ 12. Anemia. Lower pair of pinne elongated and fertile. 
* * *Sporangia large, globose, with merely the rudiments of a ring; panicled. 
13. Osmunda. Fertile portions of fronds contracted into panicles, 
I P 
