310 KEY TO THE GENERA. 
PAGE, 
++ Indusium cup-shaped, fixed be- 
neath the sorus; sori minute ona 
tooth of the ultimate pinnules ; 
fronds very finely cut. Boulder 
fern. . ‘ ‘ DICKSONIA. 229 
d. Sori and indusium “xear. 
ttt Several times louger “than 
wide, double; indusia opening 
toward each other, blade thick 
linear, extzre. Hart’s-tongue. 
SCOLOPENDRIUM. 268 
ttt Shorter, some parallel to the 
midrib, others od/zgue to it, often zx 
patrs or jotned at the ends, irregu- 
larly scattered on the underside of 
the frond; blade ¢aferzug to a 
slender tip. Walking fern, 
CAMPTOSORUS. 265 
ttt Short, strazght mostly odlzgue 
to the midrib, indusium usually 
narrow, opening foward the méa- 
vib, fronds lobed or variously 
divided. Spleenworts. 
ASPLENIUM. 155 
+++ Short; indusium more or less 
curved on the side attached to the 
frond, and when young usually ex- 
tending across a ver, robust 
species. Lady fern. ATHYRIUM. 180 
