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
A. FRUITING FRONDS WHOLLY FERTILE
(Fertile and sterile fronds entirely unlike)
|
1. Fruit in a one-sided spike in two ranks; plants very small; sterile
fronds thread-like and tortuous.
Curly Grass. Schizæa.
|
|
2. Fruit in a club-shaped, brown or cinnamon-colored spike loaded with
sporangia; fruit in early spring.
Cinnamon Fern. Osmunda cinnamomea.
| |
|
3. Fruit in berry-like, greenish structures in a twice pinnate spike, which
comes up much later than the broad and coarse pinnátifid sterile fronds.
Wet ground. Sensitive Fern. Onoclea.
|
|
4. Fruit in pod-like or necklace-like pinnæ; fertile frond pinnate; sterile
frond tall, pinnátifid; fruit late.
Ostrich Fern. Onoclea struthiopteris.
| |
B. FRUITING FRONDS PARTLY STERILE