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Smith, R.W.

Spiranthes arcisepala

Spiranthes arcisepala M.C. Pace

Appalachian Ladies' Tresses

Orchidaceae (Orchid Family)

Synonym(s):

USDA Symbol: SPAR11

USDA Native Status: L48 (N), CAN (N)

"Terrestrial, acaulescent, deciduous herb, to ca. 46 cm tall. Roots fasciculate, fleshy, slender. Leaves 1–4, basal, held upright, remaining until after anthesis, withering shortly thereafter, linear-lanceolate to slightly lanceolate, bluntly acuminate, leaf base tapered and decurrent. Peduncle glabrous, 1–2 small leafy cauline bracts occasionally present (frequently absent), quickly reducing to adpressed, clasping, lanceolate, acute bracts; spike a single row of flowers in an open to slightly tightly coiled spiral (typically appearing as 1 distinct ‘rank’), moderately to densely pubescent with blunttipped septate trichomes 0.5 mm long. Floral bracts densely pubescent, narrowly lanceolate, acuminate, concave around the ovary, to 12.3 mm long. Flowers resupinate, campanulate, slightly to moderately nodding and becoming more open with age, white, faintly to moderately fragrant with a general floral scent. Sepals free, moderately to densely pubescent with blunt-tipped capitate septate trichomes. Dorsal sepal slightly convex, slightly recurved to moderately upwardly reclined distally, lanceolate, bluntly acuminate, 8.3–10.6 mm long, 2–2.9 mm wide when flattened. Lateral sepals lanceolate, acute, slightly to strongly downwardly falcate from about 1/3 to 1/2 of their length, the tips often surpassing the lower labellum margin in profile, 8.3–9.7 mm long, 1.4–2.4 mm wide. Dorsal petals slightly concave, lanceolate, bluntly acute, slightly to strongly recurved at tips, with the dorsal sepal appearing stellate, 8.3–10.7 mm long, 2.1–2.5 mm wide when flattened. Labellum shortly clawed, free but clasping the column, keeled/concave for its length, recurved strongly downward at about 1/2 the distance from the claw to labellum apex, constricted near the recurvature and then dilating below, centrally glabrous and thickened, margin entire to very slightly undulating from the base until the area of recurvature, below point of recurvature margin becoming ruffled, margin white, central area of labellum white to extremely pale yellow back in the throat, 7.2–10.1 mm long, 4.4–5 mm wide below the callosities, 3.2–3.8 mm wide at the area of recurvature when flattened, 4.1–5.2 mm wide at widest point below recurvature; 2 basal callosities/nectar glands, white to pale yellow, conical, upright, 0.9–1.2 mm tall, with long, dense papillae at the base. Column protandrous, slightly rhombic, green, 3.6–5 mm long, with a fringe of minute glands or papillae in a thin crescent just below the stigmatic surface and with a pair of upright flaps or wings at each side and clasping the column, the wings green basally; column foot glabrous; rostellum well-developed, white to ivory, tapering to thin acute membranes at the apex; stigmatic surface glabrous, shiny; anther triangularovoid; pollinium attached to a well-developed viscidium; viscidium linear, immersed in the rostellum, leaving behind a narrow V-shaped rostellar remnant after removal, 1.6–1.8 mm long. Ovary moderately to densely pubescent with septate trichomes, green. Fruit a light brown upright ovoid capsule." (Reslit: 3176).

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