Llavea cordifolia

Llavea cordifoliaLag.
(Latin: cordis, heart, and folius, leaved, = heart leaf)

Local names: Llave´s fern, cordate-leaf llavea, helecho de la llave.

Plants terrestrial or on rocks; rhizomes usually horizontal or nearly so, compact, 2–2.5 cm diam., with scales linear-lanceolate, 0.6–1.4 cm long, entire, blackish; leaves clumped, 0.45–1.2(–1.47) m long, hemidimorphic (= partially dimorphic, the fertile leaves similar to sterile except with much narrower, longer fertile pinnae limited to the terminal 1⁄3 of the blades); petioles ca. equal in length to blade, grooved, glabrous except for large (1–3 cm long), yellowish, linear-lanceolate scales near base; leaf blades broadly ovate, mostly 3-pinnate basally, 2-pinnate apically, subcoriaceous, glabrous, with ultimate segments distinctly stalked, with veins 1–2 forked, free, extending to segment margins, the ends prominent; sterile segments ovate-deltate, 2–3 cm long, 0.8–2.2 cm wide, grayish green, marginally serrulate; fertile segments much narrower, linear, 2.5–8.5 cm long, 1–4(–5) mm wide, with inrolled margins partially covering sori; sporangia borne along the veins, so abundant as to often essentially cover the entire abaxial surface of the segments; indusium differentiated, with short glandular hairs on inside; n = 29 (Knobloch 1967; Tryon & Tryon 1982; Mickel & Smith 2004). Moist limestone bluff, 1108 m (3635 ft); in TX known only from Big Bend State Park in Presidio Co. (R.J. O’Kennon & B. Warnock, 1992, BRIT, SRSC) approx. 6.9 mi from the U.S.-Mexico border; in the U.S. known only from TX; also Mexico, Guatemala, and Costa Rica. The sole U.S. collection was sporulating on 10 May. [Allosorus karwinskii Kunze, Botryogramme karwinskii (Kunze) Fee, Ceratodactylis osmundoides J. Sm.] While the TX collection of this species was made in 1992, at the time it was thought to be an aberrant individual of an Osmunda species. The specimen remained in storage until late 2010 when its identity was realized. This represents the first known TX collection and the first report for the U.S. of this primarily Mexican species (O’Kennon & Diggs 2011). In Mexico, it occurs on rocky slopes of moist woods and cliffs (Mickel & Smith 2004). Tryon and Tryon (1982) noted, “Llavea grows in mesic canyons, or other rocky places in pine and oak woods, or in tropical forests. Sometimes it occurs on roadsides, on rock walls or in damp soil. It is principally, perhaps always, a calciophile.” It superficially somewhat resembles Osmunda regalis, royal fern, (in having very different sterile and fertile pinnae on the same leaf), but is quite different in appearance from all other TX species. Because it is known in this country from only a single station in Presidio Co., we consider this species to be of conservation concern in both TX and the U.S.

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