2. Dryopteris celsa (W. Palmer) Small (log fern) Pl. 6d; Map
Rhizome and petiole scales dark brown, concolorous or sometimes with lighter
margins, shiny, linear to ovate. Leaves 60–150 cm long, monomorphic, herbaceous
to papery. Leaf blades ovate-lanceolate in outline, tapering gradually to the
tip and broadest at or below the middle, pinnately compound above to sometimes
2 times pinnately compound below, glabrous, flat. Pinnae 1.5–17 cm long,
ovate-lanceolate to linear, the tips attenuate, the margins shallowly toothed,
the pinnules entire to deeply lobed. Basal lower segment of basal pinna about
as long as the basal upper segment and shorter than the adjacent basal segment.
Sori usually about halfway between the midribs and margins of the pinnules or
pinnule lobes, rarely closer to the midribs. Indusia glabrous, thin, usually
shriveling at maturity. Spores 48–64 mm long. 2n=164. June–September.
Uncommon in the southern Ozarks in Carter, Howell, and Oregon
Counties (eastern U.S. west to Arkansas). Along moist, shaded spring
branches and in the mesic bottoms of deep sinkholes.
Dryopteris celsa is a tetraploid taxon that resulted from past
hybridization between D. goldiana and the southeastern D. ludoviciana
(Kunze) Small. Steyermark (1963) reported this species as D. clintoniana
(D.C. Eaton) Dowell var. australis Wherry, which has since been shown to
represent the sterile, triploid backcross D. celsa ¥ D. ludoviciana
and thus is more properly treated as Dryopteris ¥australis (Wherry) Small. This
rare hybrid has been reported from only five states, including Arkansas, but is not expected to occur in Missouri. It differs
from D. celsa in having somewhat dimorphic pinnae with the fertile
pinnae narrower than the vegetative ones (a trait acquired from D.
ludoviciana, which is more strongly dimorphic). For a brief mention of a
potential hybrid with D. marginalis, see the treatment of that species.
In Missouri, D.
celsa can be quite difficult to distinguish from D. goldiana,
because the differences in leaf blade shape are sometimes not as pronounced as
in plants from other states. This is most apparent in large-leaved, older
plants. Also, in a few specimens the sori are closer to the midribs than the
margins of the pinnules. In addition to the characters in the key, the leaves
of D. celsa generally have a longer, narrower aspect than do those of D.
goldiana, and the spores are consistently smaller. Those attempting to
determine specimens in this group will need to use a combination of features to
distinguish between the two species in some cases. The rare, sterile triploid
backcross between these two taxa fortunately is not expected to occur in