Tectaria heracleifolia (Willd.)

Tectaria heracleifolia (Willd.) Underw.
(Heracleum—cow parsnip, in the carrot family, and Latin: folius, leaved, = with leaves superficially like those of Heracleum)

Local names: broad halberd fern

Rhizomes erect; leaves evergreen, clustered, to 90 cm long; petioles glabrous, sparsely scaly basally, with more than 3 vascular bundles; leaf blades monomorphic, ovate to pentagonal in outline, (12–)20–45(–50+) cm long, 1-pinnate, with 3–5(– 7) pinnae (1–3 pairs plus a single terminal pinna), thick-herbaceous to subcoriaceous, glabrous; pinnae, particularly the proximal ones, with large basal lobe(s), the margins with shallow lobes, the apices acuminate to long-attenuate; lateral pinnae } falcate; sori round, in single rows on both sides of the side veins of the pinnae, to ca. 3 mm in diam.; indusia peltate, entire, persistent; 2n = 160 (Moran 1993b). Limestone sink-holes and cave entrances, occasionally in shaded canyons or shaded rock outcrops or railroad tunnels; Edwards (Walls of Devil’s Sinkhole—Cory 35624, 35628, TAES; Correll 13420, Cory 35630, BRIT), Uvalde (Parks & Cory 33414, BRIT; Limestone sink hole—Cory & Parks 294, 1939, TEX-LL; Palmer 1919c, 1934), Irion (T. Maxwell & R. Ruiz s.n., 1974, BRIT; T. Watson 19010, TEX-LL), Comal (Lindheimer, “in the entrance of a limestone cave near New Braunsfels, in 1878”—Palmer 1934), and Mason (Turner et al. 2003) cos. on the Edwards Plateau; in the U.S. otherwise known only from FL; also West Indies, Mexico, Central and South America. Sporulating Apr–Oct. This is a tropical species whose TX locations are at the extreme n limit of the distribution of the species—it is “one of the commonest ferns at low and middle elevations in southern and eastern Mexico” (Mickel & Smith 2004). It was first collected in TX in 1847 by Lindheimer (Palmer 1934) and is rare in the state, occurring only in particular microhabitats (e.g., sink-holes, caves). An Edwards Co. site is particularly interesting—there T. heracleifolia is found on the vertical shaft wall of the 140 ft deep Devil’s Sinkhole (a collapsed limestone cavern). The leaf blades can sometimes be huge when growing under very low light conditions (e.g., “ledge 200 feet down in the Devil’s Sink Hole”—Parks & Owens s.n. 24 Sep 1941, TAES). Other than TX, the species is known in the U.S. only from extreme s Florida. Given this species’ rareness and limited distribution in TX and its occurrence in only one other state in the U.S. (FL), we consider it to be of conservation concern in TX.

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