Fronds one to three feet high, broadly lanceolate, or ovate-oblong,
tapering towards the apex, bipinnate. Pinnæ lanceolate, numerous. Pinnules
oblong-lanceolate, cut-toothed or incised. Fruit-dots short, variously
curved. Indusium delicate, often reniform, or shaped like a horseshoe, in
some forms confluent at maturity.
Widely distributed, common and varying greatly in outline. The newer
nomenclature separates the lady fern of our section into two distinct
species, which should be carefully studied.[A]
[Footnote A: See monograph by F.K. Butters in _Rhodora_ of September,
1917.]
(1) THE UPLAND LADY FERN. ATHÝRIUM ANGÚSTUM
_Asplènium Fìlix-femina_
The rootstock or rhizome of the Upland Lady Fern here pictured shows how
the thick, fleshy bases of the old fronds conceal the rootstock itself. In
the Lowland Lady Fern the rootstock is but slightly concealed by old stipe
bases, and so may be distinguished from its sister fern.
One design of such rootstocks is to store up food (mostly starch), during
the summer to nourish the young plants as they shoot forth the next spring.
The undecayed bases of the old stipes are also packed with starch for the
same purpose.
[Illustration: Rootstock of the Upland Lady Fern]
[Illustration: The same split lengthwise (From Waters's "Ferns," Henry Holt
& Co.)]
[Illustration: Sori of Lady Fern. _Athyrium angustum_]
Rootstocks horizontal, quite concealed by the thick, fleshy bases of old
fronds. Scales of the long, tufted stipes dark brown. Indusium curved,
often horseshoe-shaped, usually toothed or fringed with fine hairs, but
without glands. Fronds bipinnate, one to three feet high, widest near the
middle.
This is the common species of northern New England and the Canadian
Provinces. The fronds differ very widely in form and a great many varieties
have been pointed out, but the fern student, having first learned to
identify the species, will gradually master the few leading varieties as he
meets them.
Those growing in warm, sunny places where the fruit-dots when mature
incline to cover the whole back of the frond are called "sun forms." These
are varieties TÝPICUM and ELÀTIUS, both with the pinnæ obliquely ascending
(including variety _angustum_ of D.C. Eaton), but the latter has broader
fronds with the pinnules of the sterile fronds oblong-lanceolate, somewhat
acute and strongly toothed or pinnatifid.
[Illustration: Varieties of Lady Fern Left to right--1st and 2nd, Var.
_typicum; 3d, elatius; 4th, rubellum; 5th, uncertain, perhaps confertum_]
Var. RUBÉLLUM has the sori distinct even when mature; its pinnules stand
at a wide angle from the rachis of the pinna and are strongly toothed
or pinnatifid with obtuse teeth. This variety favors regions with cool
summers, or dense shade in warmer regions. The term RUBÉLLUM alludes to
the reddish stems so often seen but this sign alone may not determine the
variety. It occurs throughout the range of the species, being a common
New England fern. Fernald remarks that this is also a common form of the
species in southern Nova Scotia.
Among other varieties named by Butters are CONFÉRTUM, having the pinnules
irregularly lobed and toothed; joined by a membranous wing, the lobes of
the pinnules broad and overlapping, giving the fern a compact appearance;
LACINIÀTUM with pinnules very irregular in size and shape, with many long,
acute teeth, which project in various directions. "An abnormal form which
looks as if it had been nibbled when young."
These varieties are represented in the Gray Herbarium.
(2) THE LOWLAND LADY FERN