Macrothelypteris torresiana

Macrothelypteris torresiana (Gaudich.) Ching
(for Luis de Torres of the Marianas Islands, governor of Guam in 1820)

Local names: Torres’ fern, Mariana maiden fern, false maiden fern, swordfern

Rhizomes short-creeping; leaves monomorphic, evergreen; leaf blades mostly 2-pinnate-pinnatifid, broadest at base, much longer than wide, to ca. 0.85(–1.5) m long, the lower surface with costal hairs unbranched, septate, mostly over 1 mm veins of ultimate leaf segments not reaching segment margins; rachis not winged; midveins of pinnae (= costae) not grooved on upper (= adaxial) surface; sori round, medial to submedial; indusia small (less than 0.3 mm in diam.) or obscure; 2n = 124 (Smith 1993a). Along streams, damp woods, and moist areas; Newton (E. Whitehouse 23089, 1950, BRIT), Liberty (M. Schedlbauer s.n., TAMU), and Hardin (e.g., L. Rosier s.n. 1963, TEX-LL) cos. in the Pineywoods, first collected in TX in Newton Co. by Eula Whitehouse in 1950 (Correll 1951; 1956); naturalized in se U.S. from KY (Gorman et al. 2011), TN (Beck 2005), VA (Wieboldt et al. 2011), and SC s to FL w to AR and TX; also naturalized in Mexico and widely in the Neotropics. Sporulating summer and fall. Native to tropical and subtropical Asia and Africa, originally described from the Marianas Islands (Thieret 1980). [Dryopteris setigera of authors, not (Blume) Kuntze, Polystichum torresianum Gaudich., Thelypteris torresiana (Gaudich.) Alston] This species is sometimes cultivated as an ornamental, but in some areas can become invasive (e.g., in AR according to J. Peck [pers. comm.]). The name Dryopteris setigera has been misapplied to this species (e.g., Correll 1951). The first known collection of this species in the U.S. was in 1904 from Florida (Leonard 1972) and it is continuing to spread in the se part of the country (e.g., Gorman et al. 2011). At the time of its discovery in TX, Correll (1951) noted that it brought the total number of pteridophyte species known for TX to 103.

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