keys to the vascular plants of east texas - Botanical Research ...

PTERIDACEAE 365
and pous or podium, foot, referring to the rhizomes which “bear on their upper surface two rows
of slightly elevated leaf bases known as phyllopodia. This imparts the appearance of an upside-down
creeping caterpillar with its two rows of feet …”—Moran 2004)
FAMILY RECOGNITION IN THE FIELD: the single East TX species is typically epiphytic or found
growing on rocks; the discrete round sori without indusia are found in single rows on each side
of the midvein of the lobes of the deeply pinnatifid leaves; the lower leaf surfaces are conspicuously
covered with peltate scales.
REFERENCES: Weatherby 1939; Correll 1956, 1966a; de la Sota 1973; Hennipman et al. 1990; Smith
1993c.
PLEOPELTIS Humb. & Bonpl. ex Willd.
SHIELD-SORUS FERN, SCALY-POLYPODY
AA widespread but primarily neotropical genus of ca. 50 species of mostly epiphytic ferns
(Andrews & Windham 1993). Some of the species now treated in Pleopeltis were formerly included
in Polypodium (“Early pteridologists placed any fern with round, non-indusiate sori in
Polypodium”—Hoshizaki & Moran 2001). However, Pleopeltis species can be readily distinguished
by having scales (hence the common name SCALY-POLYPODY) of a distinctive type scattered
over the abaxial surface of the leaf blade (as well as many other characters differentiating
them from Polypodium) (Windham 1993e). (Greek: pleos, many, and pelte, shield, in reference to
the peltate scales covering immature sori)
REFERENCES: Andrews & Windham 1993; Windham 1993e; Moran 1998; Bush et al. 1999.
Pleopeltis polypodioides (L.) E.B. Andrews & Windham var. michauxiana (Weath.) E.B. Andrews
& Windham (sp: resembling Polypodium; var.: for André Michaux, 1746–1803, French botanist
and explorer of North America), RESURRECTION FERN, GRAY POLYPODY, TREE FERN. Usually epiphytic
or sometimes growing on rocks; stems (rhizomes) slender, widely creeping, densely
scaly; leaves monomorphic, evergreen, widely spaced; leaf blades oblong to triangular-oblong
in outline, deeply pinnatifid, to 15 cm long and 5 cm wide, thick, opaque, hygroscopic, involute
upon drying, the margins mostly entire, glabrous above except for a few scales along midvein,
densely covered with peltate scales below; sori round, discrete, in single rows on each side of the
midvein of the lobes near the margins, forming conspicuous bumps on the undersurface of
leaves; indusia absent. Usually growing on various species of trees, especially oaks, sometimes
on rocks, usually in shady damp situations; widespread in e 1/2 of TX; e U.S. from DE s to FL w
to KS and TX. Previously lumped into the genus Polypodium [as P. polypodioides (L). Watt var.
michauxianum Weath.]. The common name, RESURRECTION FERN, refers to the leaves “… which
become brown and appear dead during dry periods, but ‘resurrect’ themselves after rains and
rapidly become green and lush” (Nelson 2000). This occurs because the special peltate scales on
the lower surface of the leaf are able to absorb water and quickly channel it into the leaf. Each
scale is made up of a disk-like portion composed of numerous dead cells and a stalk of living
cells. When water is present, it is drawn into the dead cells by capillary action, then taken up
by the living stalk cells, and subsequently transported into the leaf tissue (Moran 1998, 2004).
The six known varieties of this species range from the se U.S. to Argentina and Africa (Nauman
et al. 2000). m/295
PTERIDACEAE Spreng. ex Jameson
MAIDENHAIR FERN OR BRAKE FAMILY
East TX species mostly on rocks, sometimes terrestrial (or in Ceratopteris aquatic or semiaquatic);
leaves monomorphic (rarely somewhat dimorphic or in Ceratopteris distinctly dimorphic);
leaf blades 1–4(–5) pinnate or 1–more pinnate-pinnatifid; sporangia abaxial on the