Pleopeltis polypodioides
Pleopeltis polypodioides(L.) E.G. Andrews & Windham var. michauxiana (Weath.) E.G. Andrews & Windham
(sp: resembling Polypodium, polypody, a widespread related genus; var.: for Andre Michaux, 1746–1803, French botanist and explorer of North America)
Local names: resurrection fern, gray polypody, tree fern
Usually epiphytic or sometimes growing on rocks; rhizomes slender, widely creeping, much branched, densely scaly; leaves monomorphic, evergreen, widely spaced; leaf blades deeply 1-pinnatifid, oblong to triangular-oblong in outline, to 18+ cm long and 5 cm wide, thick, opaque, strongly hygroscopic, involute upon drying, glabrous on upper surface except for a few scales along midvein, densely covered with peltate scales on lower surface, the scales obscurely clathrate (= net- or lattice-like in appearance); sori round, so sunken into leaf blade tissue as to form conspicuous bumps on the upper surface of leaves; 2n = 74 (Andrews & Windham 1993). Usually growing on various species of trees, especially oaks, sometimes on rocks, usually in shady damp situations; widespread in e 1⁄2 of TX and slightly disjunct to Uvalde Co. (Correll 1956) (e.g., Anderson Co., C.M. Rowell & J.L. Blassingame 5038, BRIT); e U.S. from DE s to FL w to KS and TX, also Mexico and Central America. Sporulating May–Nov. Previously included in 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). An astonishing 97% of the plant’s water can be lost without harm. The “resurrection” occurs because special peltate scales on the lower surface of the leaf are able to absorb water and quickly channel it into the leaf—and it is the lower leaf surface that is exposed when the leaf curls up upon drying. 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). Nauman et al. (2000) noted, “The species is represented by six varieties which range from the southeastern United States southward throughout the American tropics to Argentina and in Africa.” More recently, an additional variety was named from Mexico (as Polypodium polypodioides var. knoblochianum Mickel—Mickel & Smith 2004). Sprunt et al. (2011) suggested that recent nucleotide sequence data supports the elevation of var. michauxiana to the level of species.