This key, in illustrating each genus, follows the method of Clute in "Our
Ferns in Their Haunts," but substitutes other and larger specimens. Five of
these are from Waters' "Ferns" by permission of Henry Holt & Co.
As the indusium, which often determines the name of a fern, is apt in some
species to wither early, it is important to secure for study not only a
fertile frond, but one in as good condition as possible. For convenience
the ferns may be considered in two classes.
I
THOSE WHICH HAVE THE FRUITING PORTION IN GREENISH, BERRY-LIKE STRUCTURES
AND NOT ON THE BACK OF FRONDS