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FNA | Family List | FNA Vol. 26 | Orchidaceae | Listera

4. Listera borealis Morong, Bull. Torrey Bot. Club. 20: 31. 1893.

Northern twayblade

Neottia borealis (Morong) Szlachetko; Ophrys borealis (Morong) Rydberg

Plants 4–26 cm. Stems green, slender to stout, slightly 4-angled, succulent, glabrous. Leaves: blade green to dark bluish green, elliptic, ovate-elliptic, or lanceolate, 1.3–6 × 0.7–3 cm, apex obtuse to rounded. Inflorescences 5–20-flowered, lax, 20–90 mm; floral bracts lanceolate, ovate, or oblong, 1–3 × 0.5–1 mm, apex obtuse; peduncle and rachis glandular-pubescent. Flowers pale green, yellowish green, or bluish green with veins darker green; pedicel filiform, 3.5–7 mm, glandular-pubescent; sepals and petals strongly reflexed away from lip and column; dorsal sepal elliptic-lanceolate to linear-elliptic, 4–6 × 1.5–2.2 mm, apex obtuse to rounded; lateral sepals linear-elliptic to oblong-lanceolate, falcate, 4.5–7 × 1.4–2.3 mm, apex obtuse to rounded; petals linear to linear-oblong, falcate, 4.5–5 × 0.7–1.5 mm, apex obtuse; lip oblong, slightly narrowed in center, base with broadly rounded and bluntly angled divergent auricles, apex slightly dilated, cleft into 2 oblong or semiorbiculate lobes, with apicule in sinus; disc 3-veined, lateral veins branched and purplish, base darker green, with ridge in center, thickened along center, 7–12 × 4.2–6.5 mm, margins ciliate; column arcuate, stout, 3–4 × 1 mm. Capsules ellipsoid, 8 × 5 mm. 2n = 56.

Flowering Jun--Aug. In moist, rich humus of mossy coniferous or mixed hardwood forests, swamps, often along cold streams fed by melting snow, prefers high acidic soils; 1500--3000 m; Alta., B.C., Man., Nfld. and Labr., N.W.T., Nunavut, Ont., Que., Sask., Yukon; Alaska, Colo., Idaho, Mont., Oreg., Utah, Wash., Wyo.

In Japan Listera borealis is replaced by L. yatabei Makino, which is nearly identical except for short basal auricles. Listera borealis and L. auriculata are very similar in overall appearance; the ovaries and pedicels in L. borealis are glandular-pubescent, and in L. auriculata they are glabrous.

Leaves occur three in a whorl in Listera borealis forma trifolia Lepage.


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