Sterile portion more or less divided; fruit in racemes or panicles, rarely in spikes.

Grape Ferns. Moonwort. _Botrychium_.

II

THOSE WHICH HAVE THE FRUITING PORTION ON THE BACK OR MARGIN OF FRONDS

A. INDUSIUM WANTING

[Ill.u.s.tration]

1. Fruit-dots large, roundish; fronds evergreen. Rock species.

Polypody. _Polypodium_.

[Ill.u.s.tration]

2. Fruit-dots small, roundish; fronds triangular.

Beech Ferns. _Phegopteris_.

[Ill.u.s.tration]

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

[Ill.u.s.tration]

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_.

[Ill.u.s.tration]

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

(1) Sporangia on a continuous line; fronds large, ternate; indusium narrow.

Bracken. Brake. _Pteris_.

[Ill.u.s.tration]

(2) Sporangia in oblong sori under a reflexed tooth of a pinnule; indusium broad; rachis dark and shining. Maidenhair. _Adiantum_.

[Ill.u.s.tration]

(3) Sori in roundish or elongated ma.s.ses.

Indusium broad, nearly continuous, fronds mostly smooth, somewhat leathery, pinnate. Rock species. Cliff brakes. _Pellaea_.

[Ill.u.s.tration]

Indusium narrow, seldom continuous, formed by the margin of separate lobes or of the whole pinnules; often inconspicuous, fronds usually hairy. Lip Ferns. _Cheilanthes_.

[Ill.u.s.tration]

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_.

[Ill.u.s.tration]

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_.

[Ill.u.s.tration]

(2) Fruit-dots and indusium roundish.

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

[Ill.u.s.tration]

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

[Ill.u.s.tration]

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_.

[Ill.u.s.tration]

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_.

[Ill.u.s.tration]

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_.

[Ill.u.s.tration]

(3) Fruit-dots and indusium linear. (But see _Athyrium_.)

Very long, nearly at right angles to the midrib, double; blade thick oblong-lanceolate, entire; heart-shaped at the base. Hart's Tongue.