ebony spleenwort (Asplenium platyneuron)
SCIENTIFIC SYNONYMS: There are no scientific synonyms for
TAXONOMY: The currently accepteed scientific name for ebony
spleenwort is Asplenium platyneuron (L.) Britton, Sterns & Poggenb.
Ebony spleenwort hybridizes with several other spleenworts, partic-
ularly mountain spleenwort and walking fern.
NATIVE STATUS:Native, United States and Canada.
GENERAL BOTANICAL CHARACTERISTICS: Ebony spleenwort
is a small fern with pinnate fronds, growing in tufts, with a shiny reddish-
brown stipe and rachis. The fronds are dimorphic, with long, erect, dark
green fertile fronds, which are deciduous, and shorter, spreading, lighter
green sterile fronds, which are evergreen. The leaf blade is linear in shape, sometimes slightly wider in the upper half of the blade, measuring from 4
to 50 centimeters (2 to 20 in) long and from 2 to 5 centimeters (0.8 to 2 in)
wide, sometimes as wide as 7 centimeters (3 in). It comes to a point at its
tip and gradually tapers at its base. The blade is shiny and has a few scat-
tered hairs, or lacks them entirely. The rachis (leaf axis), like the stipe, is
reddish-brown or purplish-brown, shiny and hairless. The blade is cut into
pinnae throughout its length, from 15 to 45 pairs per leaf. The pinnae
are distinctly alternate along the rachis. They are rectangular or quadran-
gular in shape, those in the middle of the leaf blade measuring from 1 to
2.5 centimeters (0.4 to 1 in) in length and from 0.3 to 0.5 centimeters (0.1
to 0.2 in) in width. Each pinna has an obvious auricle at its base, pointing
towards the tip of the blade and overlapping the rachis. The edges of the
pinnae have rounded or small sharp teeth; they are more deeply cut in
small forms. The tips of the pinnae may come sharply or gradually to a
point. On the underside of the blade, veins are clearly visible and free
(they do not anastomose or rejoin each other). It does not spread and form
new plants via the roots. The rhizome, from 1 to 2.5 millimeters (0.04 to
0.1 in) in diameter, bears a few narrowly triangular to linear scales, black
to dark brown in color and strongly clathrate (bearing a lattice-like pattern).
The scales are 2 to 4 millimeters (0.08 to 0.2 in) long and 0.3 to 0.6 milli-
meters (0.01 to 0.02 in) wide, with untoothed margins. The stipe (the part
of the stem below the leaf blade) is 1 to 10 centimeters (0.4 to 4 in) long,
and comprises one-quarter to one-third of the length of the blade. It lacks
wings, and is a shiny reddish-brown throughout its length. Towards the
base, it has a few threadlike scales similar in color to those of the rhizome.
Starch granules are stored in tissue at the base of the stipe and, to a lesser
extent, in the rhizome, giving the bases an enlarged appearance and a firm
texture. The stipe bases are long-lived and may survive the disintegration
of the rest of the stipe and the blade. Pinnae of the fertile fronds carry from
one to twelve pairs of sori on their underside, each 1 to 2 millimeters (0.04
to 0.08 in) long. Each pair of sori forms a chevron, pointing towards the
base of the pinna along its central axis. An indusium covers each sorus;
these are whitish and translucent or silvery with a slightly toothed or erose (irregularly jagged) edge, soon withering to reveal the sori. Each sporang-
ium in a sorus carries 64 spores.
REGENERATION PROCESS: Ebony spleenwort is capable of prolifer-
ating by forming new plantlets from buds on the rachis at the base of the
plant. These allow new individuals to form at different levels when pros-
trate fronds become buried in the leaf litter. It is very rarely for more than
one bud per plant occur. Buds occurred, on average, on 1 out of 6 plants,
both on sterile and fertile fronds, and their position at the base of the low-
est pinnae made them difficult to find among the cluster of fronds. The
buds are button-like, pale in color, and appear on the upper side of the low-
est pinnae. Each bud contains a shoot and one or sometimes two leaf pri-
mordia, covered in clathrate scales, occasionally with roots if the bud has
begun to develop. Contact with soil at the plant base stimulates their de-
velopment, and the decay of their connection with the parental leaf results
in the development of a new plant.
HABITAT TYPES: Habitats include thin upland woodlands, sandy wood-
lands, sandy savannas, rocky wooded slopes, rocky cliffs and ledges (if
not too sunny and dry), small meadows in upland wooded areas, sandy
meadows, sandstone and limestone glades, and rocky banks along roads.
In the rocky habitats where this fern occurs, there may be some seepage
of ground water. Ebony Spleenwort is found in both higher quality natural
areas and more disturbed habitats such as old fields and can be found
where there has been some removal of trees or brush in wooded areas by
fire or other means).
SITE CHARACTERISTICS: Ebony spleenwort can be found at altitudes
from 0 to 1,300 meters (0 to 4,265 ft). It will tolerate soils ranging from
mediacid (pH 3.5–4.0) to subalkaline (pH 8.0–8.5), although it prefers
subacid soils (pH 4.5–5.0) over mediacid. Unlike many other North Amer-
ican spleenworts, it can grow on soil as well as rock. When growing in
soil, It can colonize a variety of rocks, particularly (but not limited to)
calcareous ones, and will also grow on mortared walls.
SEASONAL DEVELOPMENT: The spores of ebony spleenwort are re-
leased to the wind during the summer or early fall.
GENERAL DISTRIBUTION: Ebony spleenwort occurs throughout the
eastern United States, north from Florida to New England (it is absent in
much of the Canadian maritime provinces (Newfoundland, Nova Scotia,
New Brunswick). It extends west to New Mexico, then north to Colorado, Nebraska, Iowa and Minnesota. It is also found in Quebec and Ontario.. It
does not naturally occur in the northern Rocky Mountain states and Pacific
coast or northwestern states.
SKY MEADOWS DISTRIBUTION: To be determined.
IMPORTANCE AND USES: Information about floral-faunal relation-
ships is limited. Two aphids, Amphorophora ampullata and Idiopterus nephrelepidis, feed on the plant juices of spleenworts (Asplenium spp.);
and frond fragments of ebony spleenwort have been found in the gullets
of woodland jumping mice (Napaeozapus insignis insignis).
Ebony spleenwort is sold as an ornamental.
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