HYMENOPHYLLACEAE (Filmy Fern Family)

References: Farrar in FNA (1993b).

A family of 6-10 genera and 600-650 species.

1. Sporophytes present......2

1. Gametophytes only present......3

2. Indusium ("involucre") bivalvate (deeply divided into 2 flaps); receptacle not exserted from between the 2 flaps of the indusium...... Hymenophyllum

2. Indusium ("involucre") tubular or funnelform, sometimes slightly 2-lobed; receptacle long and whiplike, exserted from the mouth of the tubular indusium......Trichomanes

3. Gametophytes filamentous, no portion flattened and planar......Trichomanes

2. Leaf blade with stellate hairs......H. tayloriae

2. Leaf blade glabrous......H. tunbrigense

3. Gemmae absent; margin entire, composed predominantly of straight-sided cells; archegonia and antheridia common, often present on the same gametophyte; plant typically forming rosettes; branches always broad; proliferations few, always marginal......H. tunbrigense

Hymenophyllum tayloriae Farrar & Raine, Gorge Filmy Fern. Mt (NC, SC): spray cliffs near waterfalls, permanently moist ceilings of grottoes in escarpment gorges with high rainfall; rare (NC Watch List). This species is endemic to the escarpment gorges region of Transylvania, Jackson, and Macon counties, NC, Pickens and Oconee counties, SC, and Rabun County, GA (Davison 1997). It was recently named (in honor of the first collector), following the demonstration that it represented a gametophyte distinct from the gametophytes of any (sporophytically) known species (Raine, Farrar, & Sheffield 1991), including H. tunbrigense, present in the close vicinity. Raine, Farrar, & Sheffield (1991) point out that "H. tayloriae is distinguished from the independent gametophytes of Vittaria appalachiana Farrar & Mickel by its 2-dimensional spathulate gemmae (those of V. appalachiana are uniseriate), rhizoid attachment only to marginal cells, yellow-green color, and glossy texture. Thalloid liverworts of similar size are generally more than one cell thick or have a distinct midrib, have notched apical meristems, and do not produce spathulate gemmae." An immature sporophyte, collected by Taylor in 1936, has stalked stellate hairs on the margins and midrib of the leaf and was the only sporophytic collection of the species until the recent discovery of additional juvenile sporophytes in AL (FNA 1993b). [= FNA; "a branching ribbon-like gametophyte with marginal rhizoids and small, ovate, plate-like gemmae several cells wide, of the genus Hymenophyllum" -- RAB]

Hymenophyllum tunbrigense (Linnaeus) J.E. Smith, Tunbridge Filmy Fern. Mt (SC): moist rock faces in an escarpment gorge with high rainfall; rare (SC Rare List). June-September. The occurrence of this filmy fern in the escarpment gorge of Eastatoe Creek (and its tributaries) is remarkable. Overall, H. tunbrigense is a "Gulf Stream plant," found in highly humid, climates in the West Indies, and the maritime west coast of the British Isles. H. tunbrigense somewhat resembles Trichomanes boschianum. This species may yet be found in NC in similarly rugged and humid escarpment gorges. It differs from T. boschianum in having the sporangia not extending beyond the deeply 2-lobed involucre (as opposed to having the sporangia exserted beyond the slightly bilobed, funnelform involucre). [= RAB, FNA, K, W]

2. Leaves pinnate-pinnatifid, more than 5 cm long......T. boschianum

2. Leaves simple to slightly lobed, less than 2 cm long...... T. petersii

3. Gametophytes growing in association with or in proximity to sporophytes of T. boschianum or T. petersii T. boschianum or T. petersii (see discussion under......T. intricatum

Trichomanes boschianum Sturm, Appalachian Filmy Fern. Mt (NC, SC): on rock outcrops, usually vertical or overhanging, usually in deeply shaded grottoes receiving seepage or spray from waterfalls; rare (NC Threatened, SC Rare List). June-September. The species ranges from w. NC and w. SC west to GA, AL, and AR, and north to s. OH, KY, and s. IL; also disjunct in Chihuahua, Mexico. Documentation for the report of this species in VA (FNA) is unknown. [= RAB, C, F, FNA, G, K, S, W]

Trichomanes intricatum Farrar, Grotto-felt, Appalachian Trichomanes, Weft Fern. Mt, Pd (NC, SC, VA): on ceilings or back walls of grottoes, especially in humid gorges or near or behind waterfalls; rare (NC Watch List, VA Watch List). This species is rather widespread in e. North America, from VT, MA, and CT south and west to NC, SC, GA, AL, TN, KY, IN, and IL. T. intricatum cannot be morphologically distinguished from gametophytes of T. boschianum or T. petersii; the electrophoretic and phytogeographic evidence of Farrar (1992) leave little question, however, that it should be considered a distinct species. Although Farrar (1992) found that 30 of 30 populations of Trichomanes gametophytes "east of the Mississippi River that were not within or adjacent to sporophyte populations of T. boschianum or T. petersii" were T. intricatum, the key above (based on proximity to sporophytes) should be considered to provide only a presumptive or likely identification of gametophytes. Farrar (1992) also showed that independent gametophytes in AR were those of T. boschianum and T. petersii. Farrar (1992) points out the "intriguing possibility that somewhere in the Appalachian Mountains sporophytes of this species may yet exist." Probably the most likely area in which to search for the sporophyte generation of T. intricatum is the escarpment gorge region of NC, SC, and GA near Highlands, NC, where topography, waterfalls, and the highest rainfall east of the Cascade Mountains combine to create microclimatic conditions that have favored the relict survival of numerous species of mosses, liverworts, and ferns. Any filmy-fern sporophyte which differs from T. boschianum, T. petersii, or Hymenophyllum tunbrigense should be investigated carefully. Vittaria appalachiana and Hymenophyllum tayloriae gametophytes differ from Trichomanes intricatum in being thallose rather than filamentous. [= FNA; "a filamentous gametophyte, with spindle-shaped gemmae one cell wide but with the cells decreasing in size toward the apices, of the genus Trichomanes" -- RAB]

Trichomanes petersii A. Gray, Dwarf Filmy Fern. Mt (NC, SC): on vertical faces of rock outcrops in humid gorges, primarily of the Savannah River drainage, in the context of the very humid escarpment gorges on relatively dry rocks, not on rocks receiving substantial seepage or spray from waterfalls; rare (NC Threatened, SC Rare List). June-August. Ranging from w. NC and w. SC southwest to FL, AL, MS, and LA, and north to AR and s. IL; also in Mexico and Guatemala. This diminutive species is often overlooked, except by bryologists and hepaticologists; it does superficially resemble a moss or liverwort more than a fern. It occurs on tree bark in some parts of its range. [= RAB, FNA, K, S, W]

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Flora of the Carolinas and Virginia, Working Draft of 27 October 1997 -- KEY TO PTERIDOPHYTE GENERA. Alan S. Weakley. The Nature Conservancy, Southeast Regional Office, Southern Conservation Science Department.