This evergreen perennial fern consists of a small tuft of several
spreading leaves. The leaves are 1-7" long, ½–1½" across, and somewhat
leathery in texture; they are deltate to narrowly lanceolate-deltate in
shape and pinnatifid with 2-9 pairs of conspicuous lobes. The lobes are
up to ½" long and ½" across, becoming gradually smaller in size toward
the leaf tip; they are oval to nearly orbicular in shape and their
entire (smooth), horizontally undulate, or bluntly crenate. The margins
of adjacent lobes are narrowly separated from each other or slightly
overlapping. Sometimes there is a single pair of sessile leaflets at
the bottom of the leaf blade, rather than a pair of basal lobes. The
characteristics of such leaflets are similar to the larger lobes.
leaf bases are indented between the basal lobes (or basal leaflets,
when they are present), while the leaf tips are rounded to long,
slightly sinuous. The lobes disappear toward the leaf tips. The upper
leaf surface is medium green or olive green and glabrous, while the
lower leaf surface is about the same color or slightly more pale and
either minutely and
sparsely hairy or glabrous. The rachis of each leaf is green. The
slender petioles are 1-4" long and mostly green, except toward their
bases, where they are brown or black. The sori (spore-bearing
structures) are located on the leaf undersides where the lobes occur.
These sori are linear to slightly curved; they have indusia
(protective membranes) attached along one side. The tiny spores of this
fern are distributed by the wind. The root system consists of
that is either vertical or short-creeping; the rootstalk has slender
fibrous roots below.
This fern requires medium
shade, crevices of a vertical rock formation that is acidic (e.g.,
sandstone), and high humidity in an area that is protected from the
wind. Because of these demanding requirements, it is not normally
native Lobed Spleenwort is uncommon in the Shawnee Hills of southern
Illinois, while in the rest of the state it is rare (see Distribution
). Illinois is located near the northwestern range-limit
fern; it is found primarily in the Appalachian Mountains. The habitat
of this fern consists of crevices in vertical rock formations in
protected areas, such as large ravines, north-facing cliffs, or rocky
canyons. The rocky material in these habitats typically consists of
sandstone. This fern is found in high quality natural areas.
The larvae of a fly, Phytoliriomyza felti
leaves of this fern, while an aphid, Amphorophora ampullata
from the foliage (Spencer & Steyskal, 1986; Needham et al.,
Hottes & Frison, 1931; Blackman & Eastop, 2013).
fern is found in relatively dark locations that are difficult to
access, and its leaves are small in size, deer and other vertebrate
herbivores rarely browse on it.
Crevices of a sandstone rock formation in
This small fern is easy to overlook, and so it may be more common than
official records indicate. Lobed Spleenwort (Asplenium pinnatifidum
can be distinguished from the Walking Fern (Asplenium rhizophyllum
the presence of lateral lobes on its leaves, while the leaves of the
latter fern have neither lobes nor leaflets. Lobed Spleenwort differs
from other Spleenwort species (Asplenium
) by the absence, or near
absence, of true leaflets on its leaves (a single pair of basal
leaflets sometimes occurs). Other Spleenwort species have 2 or more
pairs of leaflets on their leaves. Lobed Spleenwort is considered a
naturally occurring hybrid of the Walking Fern and Mountain Spleenwort
This latter fern does not occur in Illinois.
Because its spores are usually fertile, rather than abortive, Lobed
is regarded as a distinct species that is able to reproduce itself.
This fern is able to hybridize with several other Spleenwort species,
producing such offspring as Trudell's Spleenwort (Asplenium ×
), Grave's Spleenwort (Asplenium × gravesii
Spleenwort (Asplenium ×
), and others. However, the spores
of these hybrid species are usually abortive.