(1) Sporangia on a continuous line; fronds large, ternate; indusium narrow.
Bracken. Brake. _Pteris_.
[Illustration]
(2) Sporangia in oblong sori under a reflexed tooth of a pinnule; indusium
broad; rachis dark and shining. Maidenhair. _Adiantum_.
[Illustration]
(3) Sori in roundish or elongated masses.
Indusium broad, nearly continuous, fronds mostly smooth, somewhat leathery,
pinnate. Rock species. Cliff brakes. _Pellæa_.
[Illustration]
Indusium narrow, seldom continuous, formed by the margin of separate lobes
or of the whole pinnules; often inconspicuous, fronds usually hairy. Lip
Ferns. _Cheilanthes_.
[Illustration]
Indusium of the reflexed edges, at first reaching to the midrib, or nearly
so; later opening out nearly flat; fruiting pinnules pod-like; sterile
fronds broad. Rock brakes. _Cryptogramma_.
[Illustration]