Thelypteris tetragona (Sw.) Small

  • Authority

    Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.

  • Family

    Thelypteridaceae

  • Scientific Name

    Thelypteris tetragona (Sw.) Small

  • Description

    Species Description - Rhizomes short-creeping, caudices ca. 1 cm diam.; fronds subdimorphic, the fertile ones erect, to 100 cm long, long-stipitate, the sterile ones shorter, arching, mostly 50–100 cm long; stipes stramineous to tan, to 60 cm x 2–5 mm, stellate-pubescent; blades herbaceous, pinnate-pinnatifid, each with a subconform terminal pinna, 25–45(–55) x 12–25(–30) cm, lacking buds in axils of distal pinnae; pinnae 6–10(–12) pairs, subopposite to alternate distally, sessile to stalked 1 mm, proximal pairs somewhat narrowed at bases, 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 to the costae; segments oblique, subfalcate, rounded at apices, ca. 4–6 mm wide; veins 6–10 pairs, the proximal pair from adjacent segments usually united at an obtuse angle with an excurrent vein to sinuses; indument on both sides of blades of mainly acicular hairs 0.1–0.3 mm long and a few minute furcate and/or stellate hairs 0.1 mm long on rachises and costae, veins and tissue between veins glabrous; sori inframedial, exindusiate; sporangia with simple hairs 0.1 mm long; 2n =144 (Fla, Jam, SLP, Ver, Chis, Trin).

  • Discussion

    Polypodium tetragonum Sw., Prodr. 132. 1788. Goniopteris tetragona (Sw.) C. Presl, Suppl. Tent. Pterid. 183. 1836. Dryopteris tetragona (Sw.) Urb., Symb. Antill. 4: 20. 1903. Type. Jamaica. Swartz s.n. (S; isotype B-Willd. 19708-3, microfiche UC!, photo US).

    Complete synonymy given in Smith (1983).

    This species occupies habitats similar to those of T. imbricata, its closest relative (which see). In addition to the differences in the key, T. tetragona usually has fewer lateral pinna pairs and the proximal pinnae are often slightly shortened and deflexed. The lowermost veins from 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 (e.g., Lorea 1758, from Michoaca´n, and Pringle 3959, from San Luis Potosi´), with some vein pairs united below the sinuses and some free or connivent at the sinuses, on the same frond. Most Mexican specimens have at least some setose sporangia. Morales O. 3 (FCME, IEB), from Guerrero, and Ortega O. et al. 857 (XAL), from Tabasco, are unusual in having small, setose, spatulate indusia. Mickel 5786 (NY) and Torres C. 10137 (MEXU), both from the same general area in Oaxaca, may be hybrids involving this species. In blade cutting (subopposite pinnae, distinct terminal pinna) and venation (one pair of veins united below each sinus, with an excurrent vein to sinus) they look most like T. tetragona, but they lack stellate hairs on all parts of the plant (including rachial grooves and rhizome scales), or have only very few furcate hairs in the rachial grooves. The Torres collection has about half its spores well formed, the other half shriveled or empty. Sousa 1486 (MEXU), from Tuxtepec, Oaxaca, has the appearance of a hybrid between T. tetragona and perhaps T. obliterata, judging by the intermediate venation and depth of cutting of the pinnae; the sporangia seem empty. Two even more problematic specimens are: Acevedo R. & Castillo C. 268 (IEB), from Edo. Veracruz, Mpio. Atoyac, Ejido La Esperanza, 750 m; and Marti´nez Caldero´n 576 (NY), from Edo. Oaxaca, Chiltepec, Tuxtepec. In blade shape (fertile only, both with subconform terminal pinnae) and cutting they appear likely to belong to subg. Goniopteris, but the blades completely lack stellate or furcate hairs. There are no indusia and the sporangia are very densely setose and appear almost acrostichoid, more so than any other species of Goniopteris known to us. Of known species, these two collections most closely approach T. tetragona, but the pinnae are subentire to shallowly lobed, and only ca. 5 mm wide. The spores appear well formed and similar to those of other species of Goniopteris (and unlike those of subg. Stegnogramma). Perhaps they represent an undescribed species, but the material at hand is inadequate and/or bizarre (i.e., outside the norm of expectation within the genus Thelypteris or subg. Goniopteris) for description.

  • Distribution

    In woods and along streams, trails, and roadsides, sometimes associated with limestone, also sometimes in coffee understory; 0–1000 m. USA (Fla); Mexico; Guat, Bel, Hond, Salv, Nic, CR, Pan; Gr & L Ant; Col, Ven, Trin, Guy, Sur, Ec, Peru, Braz, Bol.

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