KEY TO THE GENERA. 309 
PAGE. 
4. Sori various; indusium never formed 
of the margin of the frond. 
d. Sori and indusium odlong, par- 
allel with the midrib, somewhat 
sunken in the tissues of the frond ; 
indusium opening toward the mid- 
dle of the pinnules ; water-loving 
species. Chain ferns. 
WOODWARDIA. 216 
d. Sori and indusium roundesh. 
: tt Indusium feltate, fixed by the 
nail centre, evergreen species in rocky 
woods. Shield ferns. 
POLYSTICHUM. 106 
tt Indusium vexzform or cordate, 
fixed by the szzus, large, mostly 
woodland species. Wood ferns. 
ASPIDIUM, I17 
f 
’ 
tt Indusium hood-shaped, attached 
to the frond by its broad base, 
delow the -sorus and arching over 
it, soon withering ; moisture loving 
species. Bladder ferns. 
CYSTOPTERIS. 209 
++ Indusium s/ar-shaped, of a few 
irregular broad or narrow seg- 
ments fixed dezeath the sorus and’ 
enclosing it when young. Not 
easily seenin most species. Rock- 
loving plants usually somewhat 
chaffy. 
WOODSIA. 93 
