(Numbers{refer to Genera) 
O lease Indusia wanting, the sori uncovered (indusium very minute or 
4 evanescent in Athyrium) 
< Fronds ternately compound, about as broad as long 1. Phegopteris Dryopteris 
*~ Fronds once to thrice pinnatifid, distinctly longer than broad 
A 
“ Fronds merely pimnatifid once into subentire pinnse; sori at 
S tips of veins 2e Polypedium vulgare 
4 Fronds thrice pinnatifid into small decompound segments}; sori 
7) 
5 borne on back of veins below apex Se Athyrium americanum 
O 1be Indusia represented by false indusia which are the more or less 
4 altered margins of | segments (see lc) 
‘{ 2&— Fronds tomentose beneath, the sporangia imbedded in the rusty 
4 matted wool, lance-linear in outline 4, Cheilanthes gracillima 
7 2be Fronds pubescent beneath with short hairs, ternate with 3 
> coarse broad divisions (see 2c) 5e Pteridium aquilinum 
% 26 Fronds glabrous | 
+ Fronds distinctly unlike, the fertile,taller than the sterile, 
. /and with narrower divisions, nate Ga) sterile 
S « 
\ovate-oblong, obtuse. 6e Cryptogramma crispa 
a Fronds similar in outline, the fertile not differing 
markedly 
f 
o Fronds dichotomously forked with several pinnules arising 
/ from one side of the two branches, of thin 
Ad 
"texture 7e Adiantum pedatum 
‘, Fronds closely tripinnate, oblong-triangular in outline, 
_° of thickish firm texture 
a 
4 Cheilanthes siliquosa 
“ lc. True indusia present (see tips of fronds for persistent indusia) 
¢, Sori linear or curving in outline, more than twice as long as 
‘, broad 30 Athyrium filix-foemina 
Sori roundish in outline or i:crse-shoe elicscc. 
A Ne ARB go GSR 2 ROD 
