Thelypteris tetragona (Sw.) Small

  • Authority

    Mickel, John T. & Beitel, Joseph M. 1988. Pteridophyte Flora of Oaxaca, Mexico. Mem. New York Bot. Gard. 46: 1-580.

  • Family

    Thelypteridaceae

  • Scientific Name

    Thelypteris tetragona (Sw.) Small

  • Description

    Species Description - Rhizome short-creeping, caudex ca. 1 cm diam.; fronds subdimorphic, the fertile ones erect, to 1 m long, long-stipitate, the sterile ones shorter, arching; stipe stramineous to tan, to 60 cm long, 2-5 mm diam., stellate-pubescent; rachis without buds; lamina pinnate-pinnatifid with a subconform terminal segment, 2 5-45(-5 5) cm long, 12-25(-30) cm wide; pinnae 6-10(-12) pairs, subopposite to alternate distally, sessile to stalked 1 mm, lowermost somewhat narrowed at base, 7-15(-18) cm long, sterile ones mostly 2-3 cm wide, fertile ones 1-2(-2.5) cm wide, pinnatifid 0.5-0.7 of their width; segments oblique, subfalcate, rounded at apex, ca. 4-6 mm wide; veins 6-10 pairs, the basal pair usually united at an obtuse angle with an excurrent vein to sinus; costae on both sides with mainly acicular hairs 0.1-0.3 mm long; leaf tissue herbaceous, glabrous; sori inframedial, exindusiate; sporangia with simple setae 0.1 mm long; n = 72.

  • Discussion

    Polypodium tetragonum Swartz, Prodr. veg. ind. occ. 132. 1788. Dryopteris tetragona (Swartz) Urban, Symb. antill. 4: 20. 1903. Type. Jamaica. Swartz s.n. (S). Complete synonymy cited in A. R. Smith (1983). This species occupies similar habitats as Thelypteris imbricata, its closest relative (which see). In addition to the differences mentioned in the key, T. tetragona usually has fewer lateral pinna pairs and the lowermost pinnae are often slightly shortened and deflexed. The lowermost veins in adjacent segments are usually (but not always) united and produce an excurrent vein to the sinus. Even on a single frond there is often considerable variation. All Oaxacan species have at least some setose sporangia. Mickel 5786 may be a hybrid involving this species. In blade cutting (subopposite pinna, distinct terminal segment) and venation it looks most like T. tetragona, but it lacks stellate hairs on all parts of the plant (including rachis groove and rhizome scales) and the rhizome scales seem more like those found in subg. Cyclosorus.

  • Distribution

    In woods and along streams, trails, and roadsides, sometimes associated with limestone, also sometimes in coffee understory; Ixtlán, Jamiltepec, Juchitán, Juquila, Putla, Tuxtepec; 60-900 m. Mexico (Sin?, Tam, Hgo, SLP, Ver, Oax, Chis, Tab, Yuc, Camp); US (Fla); Guat to Pan; WI, Trin; Sur, Ven, Col, Ec.

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