Monographs Details: Thelypteris
Authority: Mickel, John T. & Beitel, Joseph M. 1988. Pteridophyte Flora of Oaxaca, Mexico. Mem. New York Bot. Gard. 46: 1-580.
Description:Genus Description - Terrestrial to rarely epipetric; rhizomes long-creeping to short-creeping to erect, dictyostelic; rhizome scales entire and usually ciliate on the margin and/or surface; stipes in cross section with two crescent-shaped vascular bundles at the base, these fusing distally; stipe, rachis, and costae adaxially sulcate, sulci not running continuously into axis of the next order; fronds simple to pinnate to usually pinnate-pinnatifid, to decompound (Old World groups); lamina, stipe, and/or rachis nearly always at least sparingly hairy, hairs acicular (unicellular or multicellular), hamate, or stellate; sori dorsal on the veins, occasionally submarginal, with or without reniform indusia; spores bilateral, monolete (tetrahedral and trilete in a few Old World species), with a usually prominent perispore; gametophytes cordate, usually glandular or hairy; x = 36, 35, 34, 33, 32, 31, 30, 29, 27.
Discussion:Type: Thelypterispalustris Schott [=Acrostichum thelypteris Linnaeus]. Some authors adopt Thelypteris thelypteroides (Michaux) Holub as the name for this taxon, but R. Tryon and A. Tryon (Amer. Fern J. 63: 65-76. 1973) presented an argument against this.
In its broadest sense, Thelypteris comprises nearly 1000 species, distributed pantropically but with a few species in temperate areas. There are perhaps 300 species in the neotropics. Distinguishing characters of Thelypteris include the stipe vasculature of two bundles (many bundles in dryopteroid ferns); acicular hairs on many parts of the frond; usually bilateral spores with a prominent perispore; and chromosome base numbers from 27 to 36 (x = 40, 41 in dryopteroids and athyrioids. Thelypteris sensu lato has been subdivided by some pteridologists into natural groups variously treated as genera, subgenera, or sections. Most of the New World groups can be well circumscribed using a combination of characters, and thus could stand as genera. For now, the interests of taxonomists and other biologists seem best served by adopting an inclusive genus with several subgenera. Those subgenera occurring in Oaxaca can be distinguished by the key following the references.
References: Christensen, C. 1907. Revision of the American species of Dryopteris of the group of D. opposita. Kongel. Danske Vidensk. Selsk. Skr., Natur-vidensk. Afd. VII, 4: 247-336; Christensen, C. 1913. A monograph of the genus Dryopteris. Part I. The tropical American pinnatifid-bipinnatifid species. Kongel. Danske Vidensk. Selsk. Skr., Naturvidensk. Afd. VII, 10: 55-282; Maxon, W. R. & C. V. Morton. 1938. The American species of Dryopteris, subgenus Meniscium. Bull. Torrey Bot. Club 65: 347-376; Smith, A. R. 1971. Systematics of the neotropical species of Thelypteris section Cyclosorus. Univ. Calif. Publ. Bot. 59: 1-143; Smith, A. R. 1973. The Mexican species of Thelypteris subgenera Amauropelta and Goniopteris. Amer. Fern J. 63: 116-127; Smith, A. R. 1983. Polypodiaceae-Thelypteridoideae [Fam. 14(4)]. Flora of Ecuador 18: 1-148.