hegopteris_.

[Illustration]

3. Fruit in lines on the margin of the pinnules; under surface of the
fronds covered with whitish powder.

Cloak Ferns. _Notholaena_.

B. INDUSIUM PRESENT

[Illustration]

1. Sori on the edge of a pinnule terminating a vein; sporangia at the base
of a long, bristle-like receptacle surrounded by a cup-shaped indusium.

Filmy Fern. _Trichomanes_.

[Illustration]

2. Indusium formed by the reflexed margin of the pinnules.

(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. _Pellaea_.

[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]

3. Indusium never formed of the margin of the frond. Sori various.

(1) Fruit-dots oblong, parallel with the midrib, somewhat sunken in the
tissues of the frond. Water-loving species. Chain Ferns. _Woodwardia_.

[Illustration]

(2) Fruit-dots and indusium roundish.

Indusium shield-shaped, fixed by the center. Evergreen glossy ferns in
rocky woods. Shield Ferns. _Polystichum_.

[Illustration]

Indusium cordate, fixed by the sinus. Wood Ferns. _Aspidium_.

[Illustration]

Indusium hood-shaped, fixed centrally behind the sorus and arching over it,
soon withering, often illusive. Fronds two to three pinnate, very graceful.
Moisture-loving species. Bladder Ferns. _Cystopteris_.

[Illustration]

Indusium star-shaped, of a few irregular segments fixed beneath the sorus,
often obscure. Mostly small, rock-loving plants, usually rather chaffy, at
least at the base, and growing in tufts. _Woodsia_.

[Illustration]

Indusium cup-shaped, fixed beneath the sorus, supported by the tooth of a
leaf; sporangia borne in an elevated, globular receptacle open at the top.
Fronds finely cut. Hayscented Fern. _Dennstaedtia