6. Dryopteris marginalis (L.) A. Gray (marginal shield fern)
Pl. 7a,b; Map 26
Rhizome and petiole scales orangish brown, concolorous, not shiny, linear to
ovate. Leaves 25–95 cm long, monomorphic, leathery. Leaf blades ovate to
lanceolate or narrowly elliptic in outline, pinnately compound above to usually
2 times pinnately compound below, glabrous, flat. Pinnae 1–12 cm long, narrowly
triangular to lanceolate or linear, the tips attenuate, the margins entire or
shallowly toothed, the pinnules entire to deeply lobed. Basal lower segment of
basal pinnae 1–3 times longer than the basal upper segment and longer than or
shorter than the adjacent basal segment. Sori near the margins of the pinnules
or pinnule lobes. Indusia glabrous, thick, not shriveling at maturity. Spores
41–48 mm long. 2n=82.
Scattered throughout the Ozark and Ozark Border Divisions, locally north to
Saline and Lewis Counties
(eastern U.S. west to Oklahoma, eastern Canada). Shaded ledges of bluffs
and rock outcrops, less commonly on rocky slopes of upland forests, mostly on
sandstone, but also on other acidic substrates.
This is the most widely distributed species of Dryopteris in the state.
It tolerates a broader range of moisture and light conditions than other
members of the genus in Missouri.
In the eastern Ozarks, D. marginalis sometimes grows in close proximity
to D. intermedia on sandstone ledges. The sterile, diploid hybrid
between these two diploid species, which has not been formally named, has not
been found in Missouri
but should be searched for at these sites. This hybrid has a leaf texture
similar to that of the marginal shield fern, but has a somewhat more divided
leaf blade and has the sori farther from the margins. Observation of the
malformed, irregular spores is necessary to confirm its identity.
Two other hybrids involving D. marginalis that are less likely to be
discovered in Missouri are the sterile,
diploid hybrid with D. goldiana (D. ¥neo-wherryi W.H. Wagner), which
has been reported from Illinois, and the
sterile, triploid hybrid with D. celsa (D. ¥leedsii Wherry), which is
known from Arkansas.
Both of these hybrids are large plants that resemble their other parent more
than they do the marginal shield fern and are best distinguished by their