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Appalachian Bristle Fern

Vandenboschia boschiana (J. W. Sturm ex Bosch) Ebihara & K. Iwats.

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Although earlier treated as synonymous with the tropical American Trichomanes radicans Swartz, recent authors have agreed that Trichomanes boschianum is a distinct taxon endemic to eastern North America. It exists as fertile diploids and tetraploids with occasional sterile triploids. Diploid cytotypes are prevalent in western localities, and polyploids are more common to the east. Although occurring in climatically moderated habitats, most populations suffer heavy mortality from sporadic droughts. The plants are very slow to regrow, and many populations are currently but a fraction of their size of 20 years ago. They seldom show evidence of sexual reproduction although gametophyte colonies of this species may be found in the vicinity of fertile sporophytes. Identity of these gametophytes has been confirmed by enzyme electrophoresis, but most occurrences of independent Trichomanes gametophytes in the eastern United States have been shown by this method to be those of T . intricatum (D. R. Farrar 1985).
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Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
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Flora of North America Vol. 2 in eFloras.org, Missouri Botanical Garden. Accessed Nov 12, 2008.
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Description

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Plants on rock. Stems long-creeping, slender, bearing widely spaced leaves; stems covered with dark multicellular hairs of 2 kinds, unbranched gland-tipped hairs and branched or unbranched rhizoidlike hairs, sparsely rooted. Leaves lanceolate, 1--2-pinnate-pinnatifid, 4--20 × 1--4 cm, bearing scattered short, unbranched, glandular hairs on principal veins; petioles shorter than blades. Venation pinnate, without unconnected false veins. Soral involucres terminal on lateral veins at base of lobes, conic, not flaring at mouth; involucral lips not dark-edged. Gametophytes composed entirely of branching filaments. Gemmae composed of short filaments of undifferentiated cells. 2 n = 72, 108, 144.
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cc-by-nc-sa-3.0
copyright
Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
bibliographic citation
Flora of North America Vol. 2 in eFloras.org, Missouri Botanical Garden. Accessed Nov 12, 2008.
source
Flora of North America @ eFloras.org
editor
Flora of North America Editorial Committee
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eFloras.org
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Distribution

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Ala., Ark., Ga., Ill., Ind., Ky., N.C., Ohio, S.C., Tenn., Va., W.Va.; Mexico in Chihuahua.
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cc-by-nc-sa-3.0
copyright
Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
bibliographic citation
Flora of North America Vol. 2 in eFloras.org, Missouri Botanical Garden. Accessed Nov 12, 2008.
source
Flora of North America @ eFloras.org
editor
Flora of North America Editorial Committee
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eFloras.org
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Habitat

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In deeply sheltered grottoes on noncalcareous rocks; 150--800m.
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Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
bibliographic citation
Flora of North America Vol. 2 in eFloras.org, Missouri Botanical Garden. Accessed Nov 12, 2008.
source
Flora of North America @ eFloras.org
editor
Flora of North America Editorial Committee
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eFloras.org
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Vandenboschia boschiana

provided by wikipedia EN

Vandenboschia boschiana, synonym Trichomanes boschianum,[1] the Appalachian bristle fern[2] or Appalachian filmy fern, is a small delicate perennial leptosporangiate fern which forms colonies with long, black creeping rhizomes. The evergreen fronds are bipinnatifid, deeply and irregularly dissected, about 4 to 20 cm long, 1 to 4 cm across with winged stipes 1 to 7 cm long and light green in colour. The common name derives from the leaves which are very thin, only a single cell thick, missing an epidermis and translucent, giving the appearance of a wet film.

Sori, the spore-producing organs are formed along the margins of the frond segments. The indusium forms a funnel around the sorus which is sunken in the leaf tissue. A bristle-like receptacle protrudes from the indusium as in all Trichomanes species. Spore production occurs between July and September.

In common with all ferns, V. boschiana exhibits a gametophyte stage in its life cycle (alternation of generations) and develops a haploid reproductive prothallus as an independent plant. In contrast to the typical heart-shaped fern prothallus, V. boschiana gametophytes are filamentous and resemble colonies of green algae or moss protonemata.

Taxonomy

According to the Flora of North America ploidy is rather variable. The western colonies tend to be diploid whilst the eastern ones are mostly tetraploid. Sterile triploids have also been recorded.

It has been hypothesized that most of the populations of V. boschiana are genetically identical clones of great age.[3]

Distribution

Endemic to eastern North America. A single disjunct population has been found in Chihuahua, Mexico. Populations are found in the eastern United States from southern Ohio in the north to Alabama in the south and from Arkansas and southern Illinois in the west to South Carolina in the east. In all areas the populations are very scattered and reflect the distribution of an uncommon habitat.

Ecology and conservation

Vandenboschia boschiana is found in deep shade on damp acid rocks, usually sandstone, of sheltered canyons, grottos and rock shelters at an altitude of 150 to 800 m. The rock outcrops are generally found within mesic upland forests.[3]

This fern is dependent upon a constantly high air humidity which places severe restrictions on its distribution in the current climate of eastern North America. In fact V. boschiana is believed to be a relict of milder pre-glacial conditions.[3] The current distribution of V. boschiana is considered to reflect historical lack of glaciation, substrate, type of bedrock, lack of disturbance in the surrounding forest and micro-climate. Temperature is perhaps less important than these factors though extreme cold weather can apparently cause mortality.[4] Periodic droughts do cause heavy mortality and have reduced many population sizes over the last few decades.[5]

The species is probably more at risk than its G4 grading would suggest and state NatureServe conservation rankings are Vulnerable (S3) to Critically imperiled (S1).

Hazards include drying of the habitat, removal of forest canopy shading the rock exposures and over-collecting.[4]

Cultivation and uses

The plant is not known to be widely cultivated. From its large-scale distribution the plant may be hardy to USDA Zone 6, although this may not reflect the micro-climate of its sheltered habitat.

References

  1. ^ a b c Hassler, Michael & Schmitt, Bernd (August 2019). "Vandenboschia boschiana". Checklist of Ferns and Lycophytes of the World. 8.10. Retrieved 2019-10-08.
  2. ^ USDA, NRCS (n.d.). "Trichomanes boschianum". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 14 December 2015.
  3. ^ a b c Hill, S.R. (2003). Conservation Assessment for Appalachian Bristle Fern (Trichomanes boschianum) Sturm. USDA Forest Service, Eastern Region
  4. ^ a b Cusick, A. (1983). Trichomanes boschianum in Ohio. Ohio DNR
  5. ^ Farrar, D.R. (1993). Hymenophyllaceae, In: Flora of North America Editorial Committee, eds., Flora of North America, Vol. 2. Oxford University Press. New York.

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Vandenboschia boschiana: Brief Summary

provided by wikipedia EN

Vandenboschia boschiana, synonym Trichomanes boschianum, the Appalachian bristle fern or Appalachian filmy fern, is a small delicate perennial leptosporangiate fern which forms colonies with long, black creeping rhizomes. The evergreen fronds are bipinnatifid, deeply and irregularly dissected, about 4 to 20 cm long, 1 to 4 cm across with winged stipes 1 to 7 cm long and light green in colour. The common name derives from the leaves which are very thin, only a single cell thick, missing an epidermis and translucent, giving the appearance of a wet film.

Sori, the spore-producing organs are formed along the margins of the frond segments. The indusium forms a funnel around the sorus which is sunken in the leaf tissue. A bristle-like receptacle protrudes from the indusium as in all Trichomanes species. Spore production occurs between July and September.

In common with all ferns, V. boschiana exhibits a gametophyte stage in its life cycle (alternation of generations) and develops a haploid reproductive prothallus as an independent plant. In contrast to the typical heart-shaped fern prothallus, V. boschiana gametophytes are filamentous and resemble colonies of green algae or moss protonemata.

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