Spiranthes parksii Correll, Amer. Orchid Soc. Bull.

Pace, Matthew C. & Cameron, Kenneth M., 2017, The Systematics of the Spiranthes cernua Species Complex (Orchidaceae): Untangling the Gordian Knot, Systematic Botany (Basel, Switzerland) 42 (4), pp. 1-30 : 10-11

Spiranthes parksii Correll, Amer. Orchid Soc. Bull. 16: 400, f. 1–6. 1947.—TYPE: U. S. A. Texas: Brazos County, Democrat Bridge, Navasota River, collected 19 October 1945, Parks s.n. (holotype: AMES!).

Spiranthes cernua is most similar to S. arcisepala , S. incurva , and S. ochroleuca . It can be distinguished from these species by its upward sweeping lateral sepals (vs. downwardly arching in S. arcisepala ), centrally thinner labellum, distribution along the Coastal Plain and southern Appalachian Mountains (vs. centrally thickened labellum and occurrence in the Interior Lowlands and northern Appalachian Mountains in S. incurva ), and white to pale-yellow abaxial labellum coloration and abaxial surface with conical, highly reduced glands (vs. abaxial yellow to golden coloration and abaxial surface with spherical glands in S. ochroleuca ).

Terrestrial, acaulescent, deciduous herb, to ca. 100 cm tall. Roots fasciculate, fleshy, slender. Leaves 1–5, basal, held upright, remaining until after anthesis (occasionally fugacious at anthesis), withering shortly thereafter, linear-lanceolate to lanceolate, 5–22 cm long, 5–8 mm wide, bluntly acuminate, leaf base tapered and decurrent. Peduncle glabrous, 1–3 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 tightly coiled spiral (appearing as 1–4 ‘ranks’), moderately to densely pubescent with blunt-tipped septate trichomes to 0.5 mm long. Floral bracts pubescent, lanceolate, acuminate; concave around the ovary, 7–14 mm long. Flowers campanulate, slightly to strongly nodding (more so with age), white to pale ivory, lightly fragrant with a general floral odor or not fragrant (some coastal populations exhibit strong general floral fragrance). 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, 6–12 mm long, 3 mm wide when flattened. Lateral sepals lanceolate, acute, straight to just barely falcate, angled slightly outward and upward, the tips often incurved, surpassing the dorsal sepal and petals, 6–12 mm long, 2 mm wide. Dorsal petals slightly concave, lanceolate, bluntly acute, slightly to strongly recurved at tips, with the dorsal sepal appearing stellate, 6–12 mm long, 3 mm wide when flattened. Labellum shortly clawed, free but clasping the column, keeled/concave for its length, recurved strongly downward at about 1/3 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, white but rarely centrally pale yellow, 7–13 mm long, 3–6 mm wide below the callosities, 2–6 mm wide at the area of recurvature when flattened, apex acuminate; 2 basal callosities/nectar glands, white to pale yellow, conical, upright, 1–2 mm tall, with long, dense papillae at the base. Column protandrous, slightly rhombic, green, 4.1–6 mm long, 2–2.5 mm wide, 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; column foot glabrous; rostellum well-developed, white to ivory, tapering to thin acute membranes at the apex, 1.2–1.5 mm long; stigmatic surface glabrous, shiny, 1–2 mm long, 1.5–2.5 mm wide; anther triangular-ovoid; pollinium attached to a well-developed viscidium; viscidium linear, immersed in the rostellum, leaving behind a narrow V-shaped rostellar remnant after removal, 1–1.8 mm long. Ovary moderately to densely pubescent with septate trichomes. Fruit a light brown upright ovoid capsule. Figures 1 and 2 .

In its new strict sense, S. cernua ( Figs. 1 , 2 ) occurs from the Coastal Plain to the eastern and southern Appalachian Mountains, southern Interior Lowlands, and Cumberland Plateau ( Fig. 14 ). Within S. cernua s. s., we here formally synonymize S. parksii under S. cernua as a localized sub-peloric form promulgated through apomixis, supporting the work of Dueck and Cameron (2007, 2008b), Dueck et al. (2014), Pace and Cameron (2016), and Pace et al. (2017). As exemplified by this synonymization, S. cernua s. s. is still a morphologically variable species ( Figs. 1 , 9 ), although less so than previously defined. Some populations, such as the former S. parksii , exhibit small-sized reduced flowers in an open spiral, whereas others, particularly in the Mid-Atlantic region from southern New York to coastal Virginia, display large flowers nearly 1 cm in length held in a very tight spiral (appearing as 3–4 separate ranks), with a complete gradation between these two extremes. In contrast to this morphological variability, S. cernua s. s. is consistent in its habitat preferences, occurring in essentially wet, short-statured, open graminoid-cyperoid locations: mossy seeps, maritime dune swales, Sphagnum L. dominated lake and pond edges, wet meadows, roadsides, and open savannas ( Fig. 15 ). Spiranthes cernua s. s. is typically faintly fragrant with a general floral odor, although some populations are strongly fragrant, whereas others appear to entirely lack a perceivable fragrance.

Figures

FIG.1. Spiranthes cernua s. s. A. New Castle Co., Delaware, sample sc1. B. Worchester Co., Maryland, sample sc8d. C. Wayne Co., Georgia, sample sc15. D–E. Sussex Co., Delaware. F. Cape May Co., New Jersey, sample sc6. G. Scott Co., Arkansas, sample sc29; flowers reduced (sub-peloric) and partially closed. H. Towns Co., Georgia; photo: James Fowler, used with permission.I. James City Co., Virginia, sample sc9. J. Lexington Co., South Carolina. K. Pike Co., Alabama. L. Co-occurring S. 3kapnosperia (L) and S. cernua (R), Jackson Co., North Carolina; scale bars denote cm.

FIG.2. Spiranthes cernua s. s. A.Habit.B.Inflorescence.C.Flower and floral bract in profile.D–G.Flower, dissected view.D. Dorsal sepal. E.Dorsal petal. F.Lateral sepal.G.Labellum.H. Labellum, column, and ovary in natural position.I–K. Column.I. Dorsal and ventral views.J. Profile. K. Anther. L. Pollinia. Drawn from Pace 612 and Pace 615 by Bobbi Angell.

FIG.14. Distribution maps of the S. cernua species complex s. s., based on herbarium specimens and phylogenetic sampling.A.S. arcisepala, S. cernua s. s., S. incurva, S. 3kapnosperia, S. niklasii. B. S. casei and S. ochroleuca. Maps produced by Elizabeth Kiernan, New York Botanical Garden GIS Lab.

FIG. 9. Boxplot comparisons of select labellum characters for the Spiranthes cernua species complex s. s. and hybrids. A. Callosity (nectar gland) height (mm). B. Labellum length (mm). C. Width of lower labellum (mm).

FIG. 15. A–B. Habitat of S. cernua s. s. A. Marshy pond edge, with Nyssa sylvatica Marshall, Chamaecyparis thyoides (L.) Britton, Sterns & Poggenb., Sarracenia L., and Eriocaulon L., Lexington Co., South Carolina. B. Seeping, graminoid-cyperoid and brushy roadside, mixed with S. 3kapnosperia (type location), Transylvania Co., North Carolina. C–E.Habitat of S. incurva. C. Xeric roadside slope, with Solidago nemoralis Aiton and Andropogon gerardi Vitman, Orleans Co., Vermont; sample location of soch10. D. High diversity fen, Clark Co., Ohio, sample location of sc32a. E. Sandy, xeric dune swales and back dunes, co-occurring with S. magnicamporum (with Mr. S. Martella), Lake Co., Illinois. F. Habitat of S. niklasii; xeric, prairie-like opening, Greene Co., Arkansas, sample location of AR1. G–H. Habitat of S. arcisepala. G. Seeping fen, McKean Co., Pennsylvania. H. Type location; roadside ditch and Sphagnum seep with Eriophorum virginicum L. under a power-line cut, Hamilton Co., New York.