Spiranthes incurva (Jenn.) M.C. Pace, 2017

Spiranthes incurva (Jenn.) M.C. Pace View in CoL , comb nov. [ancient Spiranthes cernua 3 Spiranthes magnicamporum ], Ibidium incurvum Jenn., Ann. Carnegie Mus. View in CoL 3: 483. 1906.—TYPE: U. S. A. Pennsylvania: Erie County, Presque Isle. Sandy margins of pond near Fog Whistle, collected 26 August 1905, Jennings s.n. (Lectotype: CM!; isolectotypes: Jennings

s.n., 18, 26 August 1905, CM!, NY !; syntypes: Jennings s.n., 24 Aug 1905, Jennings s.n., 18, 9780, 25 August 1905, MICH!, MIN!, NYS!, PH !; paratypes included by Jennings (1906): Shafer 29, 9781 9–11 September 1900, CM!, MUHW!, PH!, Gutenberg s.n. 16 August 1880, CM!). Note: Catling, via an annotation label, designated Jennings s.n., 26 Aug 1905, as the “ holotype.” Since Jennings selected a suite of specimens, “ Aug. 24–26, 1905 ”, housed at CM as “the type specimens”, and not a specific specimen, collection number, or sheet, the specimen designated by Catling is more properly designated as the lectotype. All other specimens collected on Aug. 26, 1905 must then be isolectotypes, and all other specimens collected within “the type specimens” collection range designated as syntypes, as above. Jennings’ collection number 18 appears multiple times on differing days .

Spiranthes incurva is most similar to its parental species: S. cernua s. s. and S. magnicamporum . It can be distinguished from S. cernua s. s. by its thickened central labellum, more narrowly lanceolate floral parts, frequently more stellate and ascending flowers, and more northern and western distribution, and it can be distinguished from S. magnicamporum by its larger callosities, slightly earlier flowering period, and non-papillate, paler labellum.

Terrestrial, acaulescent, deciduous herb, ca. 40 cm tall. Roots fasciculate, fleshy, slender to slightly tuberous. Leaves 1–5, basal, held upright, occasionally remaining until anthesis and withering shortly thereafter but more frequently absent at anthesis, linear-lanceolate to lanceolate, 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 a moderately to tightly coiled spiral (appearing as 1–4 “ranks”), moderately to densely pubescent with blunt-tipped septate trichomes to 0.5 mm long. Floral bracts moderately to densely pubescent, lanceolate, acuminate, concave around the ovary, 9.5–9.7 mm long. Flowers slightly tubularly campanulate, slightly ascending to moderately nodding, white to pale ivory. Sepals free, moderately to densely pubescent with blunt-tipped capitate septate trichomes. Dorsal sepal slightly convex, slightly to strongly recurved near the tip, lanceolate, bluntly acuminate, 8.6–10.9 mm long, 2–2.6 mm wide when flattened. Lateral sepals lanceolate, acute, straight to just barely upwardly falcate, angled slightly upward, the tips often meeting the dorsal sepal and petals, 7.7–10.7 mm long, 1.7–2.3 mm wide. Dorsal petals slightly concave, lanceolate, bluntly acute, slightly to strongly recurved at tips, with the dorsal sepal appearing stellate, 8.1–10.5 mm long, 1.8–2.2 mm wide when flattened. Labellum minutely clawed, free but clasping the column, keeled/concave for its length, recurved strongly downward at about 1/3 to 1/2 the distance from the claw to labellum apex, centrally glabrous, margin entire to very slightly undulating from the base until the area of recurvature, below point of recurvature margin becoming shallowly laciniate and crisped, margin white, central area of labellum white to very pale yellow, labellum 7.4–9.9 mm long, 3.7–5.4 mm wide below the callosities, 3.3–3.9 mm wide at the area of recurvature when flattened, 1.8–4.5 mm wide at midpoint below recurvature, apex acuminate; 2 basal callosities/nectar glands, white to yellow, very small, conical to rounded mounds, upright, 0.3–0.8 mm tall, with long, dense papillae at the base. Column protandrous, slightly rhombic, green, 3.3–5 mm long, with a fringe of minute glands or papillae in a thin crescent just below the stigmatic surface, with a pair of upright flaps or wings at each side and clasping the column, the wings green basally, becoming white to translucent; column foot glabrous; rostellum well-developed, white to ivory, becoming dark brown with age, tapering to thin acute membranes at the apex, 1.2–1.8 mm long; stigmatic surface glabrous, shiny; anther dark coffee-brown, triangular-ovoid; pollinium attached to a well-developed viscidium, yellow; viscidium linear, immersed in the rostellum, leaving behind a narrow V-shaped rostellar remnant after removal, 1.2–1.5 mm long. Ovary moderately to densely pubescent with septate trichomes. Fruit a light brown ovoid capsule. 2 n 5 45 –60. Figures 12 View FIG and 13 View FIG .

ETYMOLOGY—As in Jennings’ original description, ‘ incurva ’, from the Latin, refers to the incurved callosities of this species of hybrid origin. This feature is a key character to distinguish this species from the frequently co-occurring S. magnicamporum , one of its parental species, which has highly reduced, non-incurved callosities (the callosities of some S. incurva may approach the highly reduced callosities of S. magnicamporum ). We suggest the common name “Sphinx ladies’ tresses” for this species. The Sphinx is a hybrid mythological creature prone to enigmatic and intractable questions; similarly, the inclusion of hybrid S. incurva within the traditional concept of S. cernua has long been a major source of the latter’ s morphological variation, and strongly contributed to the idea that a proper delimitation of the S. cernua species complex was intractable.

Spiranthes incurva ( Figs. 12 View FIG , 13 View FIG ) represents likely ancient S. cernua s. s. 3 S. magnicamporum , and entirely replaces S. cernua in the middle, northern, and eastern Interior Lowlands, Western and Northern Appalachian Mountains and Adirondacks, Great Lakes Basin, and Prairie Peninsula, from New Brunswick, southern Ontario, and southern Quebec, west to Minnesota, central Nebraska, and eastern Kansas ( Fig. 14 View FIG ). In addition to the geographic differentiation, S. incurva has a centrally thickened labellum, shorter callosities, a more lanceolate labellum, and narrower leaves, vs. S. cernua s. s. which has a labellum which is not centrally thickened, longer callosities, a more oblong labellum, and wider leaves. Due to their morphological similarities and occasional to frequent cooccurrence, S. incurva has been confused with S. magnicamporum and S. ochroleuca . These three species can be distinguished from one another by flowering time, labellum surface texture, and floral shape and color: S. incurva displays white, stellate to pseudo-campanulate flowers with smooth labella in full bloom just as S. magnicamporum is reaching anthesis with ivory-colored more tubularly-shaped flowers with papillate labella, whereas the abaxial labellum coloration of S. ochroleuca is yellow to butterscotch colored, and the ivory-colored flowers are typically strongly pseudo-campanulate ( Figs. 3 View FIG , 13 View FIG ). Although it typically occurs in more xeric habitats than S. cernua s. s., S. incurva has varied habitat preferences: submerged in shallow lake dune pools, fens, bogs, rocky ice-scour meadows, lake edges, wet to xeric roadsides and prairies, alvar escarpments, and xeric rolling lake dunes composed of pure sand ( Fig. 15 View FIG ). The fragrance of S. incurva is similar to S. cernua s. s. in odor and intensity, lacking the strong vanilla-licorice fragrance of S. magnicamporum ; occasional populations are slightly malodorous.