Trichomanes boschianum
Trichomanes lineolatum
Appalachian bristle fern, Appalachian filmy fern
lined bristle fern
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.
long-creeping, threadlike, bearing scattered leaves, covered with dark hairs of 2 types, 2-celled glandular hairs and elongate rhizoidlike hairs;
roots absent.
composed of short filaments of undifferentiated cells.
lanceolate, 1–2-pinnate-pinnatifid, 4–20 × 1–4 cm, bearing scattered short, unbranched, glandular hairs on principal veins;
petioles shorter than blades.
round to obovate, simple to irregularly lobed, 1–3 × 0.5–1.5 cm, with dark stellate hairs on margin, 2-celled glandular hairs on petioles and veins, and dark rhizoidlike hairs on petioles;
petioles shorter than blades.
composed entirely of branching filaments.
unknown, presumed to be as others of subgenus.
pinnate, without unconnected false veins.
repeatedly forking from the base; unconnected false veins few or absent.
involucres terminal on lateral veins at base of lobes, conic, not flaring at mouth;
involucral lips not dark-edged.
involucres 1–5 per leaf, terminal on blades, narrowly conic, not flaring at mouth;
involucre lips with conspicuous dark marginal band 2–5 cells wide.
= 72, 108, 144.
= 68.
Trichomanes boschianum
Trichomanes lineolatum
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).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Trichomanes lineolatum leaves have unusually thick veins that are enlarged toward the margin and conspicuous in dried specimens.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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