Listera caurina |
Listera auriculata |
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northwest twayblade, northwestern twayblade |
auricled twayblade |
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Habit | Plants 5–30 cm. | Plants 5–25 cm. | ||||||||
Stems | green, succulent, glabrous. |
pale green, succulent, glabrous. |
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Leaves | blade green, ovate to elliptic, 2.5–7 × 1.8–4.5 cm, apex rounded to obtuse or subacute. |
blade pale green, suborbiculate to suborbiculate-ovate or elliptic-ovate, 2.5–6 × 1.5–4.2 cm, apex subobtuse. |
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Inflorescences | 5–30-flowered, lax, 50–130 mm; floral bracts rhombic-ovate to lanceolate, apex acute to acuminate, glabrous to slightly glandular; peduncle and rachis glandular-pubescent. |
5–20-flowered, lax, 20–100 mm; floral bracts broadly elliptic to oblong-lanceolate, 2–7 × 1–2 mm, apex obtuse; peduncle and rachis densely glandular-puberulent; bracts, pedicel, and ovary glabrous to rarely glabrate. |
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Flowers | yellowish green, small; pedicel filiform, 4–12 mm, glandular-puberulent; sepals and petals distinct and free, spreading, only slightly reflexed; dorsal sepal linear-lanceolate to lanceolate, 2.8–4 × 0.5–0.8 mm, apex acute to acuminate; lateral sepals linear-lanceolate to lanceolate, falcate, 2.8–4 × 0.5–0.8 mm, apex acute to acuminate; petals linear to linear-lanceolate, slightly falcate, 2.8–3.5 × 0.5–0.8 mm, apex acute to acuminate; lip sessile, cuneate to obovate, 4.5–6 × 2–4.5 mm, apex rounded to retuse, apiculate, apical margin slightly erose or crenulate; disc with pair of dark green stripes, each swollen at base and with small horn 1 mm from top of each swelling; column short, 1.5–2 × 1 mm. |
pale green to blue-green, fading whitish with age; pedicels stout, 2.5–5 mm, glabrous, rarely glabrate; sepals and petals reflexed away from column and lip; dorsal sepal elliptic-obovate, 3–3.5 × 1.5–2 mm, apex subobtuse; lateral sepals elliptic, oblong, or ovate-lanceolate, strongly falcate, 3–4 × 1–1.5 mm, apex subobtuse to acute; petals linear-oblong to linear, falcate, 3–3.7 × 0.8 mm, apex obtuse; lip obovate to oblong, base of lip with auricles curving around and clasping base of column, apex slightly expanded, cleft approximately 1/5–1/3 its length, forming 2 broadly rounded lobes, margins ciliate; disc 3-veined with lateral veins branched, base with ridge in center; column arcuate, 2.5–3.3 × 1 mm, dilated at distal end. |
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Capsules | semierect, ovoid to subglobose, 5 × 4 mm, glabrous. |
horizontal to semi-erect, ellipsoid, 8 × 4 mm. |
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2n | = 34. |
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Listera caurina |
Listera auriculata |
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Phenology | Flowering late Apr–Sep. | Flowering late Jun–Aug. | ||||||||
Habitat | Dry litter of mixed and coniferous forests, dense moist, coniferous forests, and on boggy wooded slopes, also damp to wet conditions on moss-covered rocks or in mossy soil | Alluvial soils in low, moist, hardwood forests or mixed hardwood-coniferous forests, shrub swamps, sphagnum bogs, requires soil that remains cool throughout summer, with high degree of acidity | ||||||||
Elevation | 100–2200 m (300–7200 ft) | 0–1000 m (0–3300 ft) | ||||||||
Distribution |
AK; CA; ID; MT; OR; WA; AB; BC
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ME; MI; MN; NH; NY; VT; WI; MB; NB; NL; NS; ON; PE; QC
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Discussion | Leaves of Listera auriculata forma trifolia (Lepage) Lepage are three in a whorl. Listera auriculata crosses with L. convallarioides to produce a natural hybrid L. ×veltmanii Case, originally discovered by H. S. Veltman and F. W. Case in 1962. The hybrid is almost exactly intermediate between its putative parents, and it is usually associated with one or the other parent (P. M. Catling 1976). Occasionally it appears to backcross with the parent species. Plants of the hybrid, although intermediate between the two putative parents, frequently differ from the parents in being much taller (to 2.5 dm). Also, the glandular pubescence of the pedicels and ovaries of the hybrid is shorter and sparser than that of the rachis; in L. convallarioides the glandular pubescence is as dense and long on pedicels as on the rachis, continuing on the ribs of the ovary. Pedicels and ovaries of L. auriculata are glabrous. The hybrids may be distinguished by using the following key. Listera ×veltmanii flowers in July and August. Its habitat is intermediate between those typical of the parents and apparently is often disturbed; 500–800 m. It is known from New Brunswick, Newfoundland and Labrador, Quebec, Ontario, Michigan, and Wisconsin. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 26, p. 591. | FNA vol. 26, p. 589. | ||||||||
Parent taxa | Orchidaceae > subfam. Epidendroideae > tribe Neottieae > subtribe Limodorinae > Listera | Orchidaceae > subfam. Epidendroideae > tribe Neottieae > subtribe Limodorinae > Listera | ||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Synonyms | L. retusa, Neottia caurina, Ophrys caurina | Bifolium auriculatum, Neottia auriculata, Ophrys auriculata | ||||||||
Name authority | Piper: Erythea 6: 32. (1898) | Wiegand: Bull. Torrey Bot. Club 26: 166, plate 356, fig. 2. (1899) | ||||||||
Web links |
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