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Description:
Peters' filmy fern, also known as bristle fern, dwarf filmy fern, or dwarf bristle fern, is a rare mat-forming fern resembling a moss or liverwort rather than a fern (Weakley 2002, USDA NRCS. 2002, and Snyder, Jr and Bruce 1986). The threadlike rhizomes are less than 0.3 millimeters (mm) in diameter and covered with short, black trichomes (hairs) (Radford et. al. 1986). The leaves of Peters' filmy fern vary in size from approximately 0.5 to 2.5 centimeters (cm) in length with the petioles equalling or exceeding the length of the blades. The thin, fragile, translucent leaves are one cell thick between the leaf veins (Thieret 1980 and Radford et. al. 1986). The leaf blades are simple, elliptic to obovate, entire, sinuate, or sometimes irregularly shallowly lobed. The leaf venation is alternate and forked and the leaves exhibit a strong mid-vein. The leaf margins, particularly in juvenile specimens, exhibit scattered, small, black hairs. The sporangia are located within funnel-shaped "involucres" occurring on the leaf tips, numbering one per leaf. The bristle or "recepticle", to which the sporangia are attached, may project as much as 5 mm from the involucre (Thieret 1980).
Habitat:
Peters' filmy fern inhabits moist, sheltered rocks, predominantly sandstones, where the surrounding air is perpetually moist. The species is rarely found on the shaded portion nearest the ground of tree trunks (Snyder, Jr and Bruce 1986). In the Florida Parishes of Louisiana, Peter's filmy fern is found on the bark of trees inhabiting moist forests. Tree species reported to provide habitat for Peters' filmy fern include southern magnolia (Magnolia grandifolia), and American beech (Fagus grandifolia) as well as various evergreen shrubs in forests near streams. The habitat of Peters' filmy fern is one of relatively high humidity forming mats up to 900 square cm, particularly on southern magnolias and typically within one meter from the base of the tree. Associate plant species include several species of liverworts and mosses, green fly orchid (Epidendrum conopseum), and resurrection fern (Pleopeltis polypodioides ssp. michauxiana) (Thieret 1980).
Range:
Peters' filmy fern is confined to the southeastern United States (Snyder, Jr and Bruce 1986). Weakley (2002) reports the species is found on vertical faces of rock outcrops in humid gorges, primarily within the Savannah River Drainage, in the context of the very humid escarpment gorges on relatively dry rocks, not on rocks receiving substantial seepage or spray from waterfalls. The species ranges from western North Carolina and western South Carolina southwest to Florida, Alabama, Mississippi, Louisiana, and north to Arkansas and southern Illinois. The species has also been found in Mexico and Guatemala. The species is often overlooked except by experienced hepaticologists and bryologists (Weakley 2002).
References
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