(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. _Dennstædtia_.
[Illustration]
(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.
_Scolopendrium_.
[Illustration]
Shorter and irregularly scattered on the under side of the frond, some
parallel to the midrib, others oblique to it, and often in pairs or joined
at the ends; blade tapering to a slender tip. Walking Fern. _Camptosorus_.
[Illustration]
Short, straight, mostly oblique to the midrib. Indusium rather narrow,
opening toward the midrib, fronds lobed or variously divided. Spleenworts.
_Asplenium_.
[Illustration]
Short, indusium usually more or less curved and frequently crossing a vein.
The large spleenworts including Lady Fern. _Athyrium_.