keys to the vascular plants of east texas - Botanical Research ...

SPIRANTHES/ORCHIDACEAE
779
mm wide, adherent apically with apex of middle sepal; lip white with a green conspicuously
concave center, clawed, suborbiculate, with a long, pointed apex, 5–7 mm long and 4–7 mm
wide (when flattened); column 4–5 mm long; pollinia 4, yellow; capsules ellipsoid, 8–13 mm
long, ca. 5 mm wide. Along wooded streams and around sloughs and ponds, usually near limestone
outcrops or in calcareous soils (e.g., Fleming Formation at Davis Hill State Park in Liberty
Co.—Liggio 2002); Jasper, Liberty (BRIT), and San Jacinto (SHSU) cos. in s part of Pineywoods; se
U.S. from VA s to FL w to TX. Sep–Oct. [Arethusa racemosa Walter] The combination of oblique
lateral petals and non-resupinate lip is distinctive. In Florida, the species is self-compatible but
not autogamous; natural fruit set was 35% in one population (Ackerman 1995). Small halictid
bees have been observed visiting the flowers (Luer 1972). While not officially designated as
such (e.g., TOES 1993; Carr 2002d; Poole et al. 2002), given its limited distribution in the state,
we consider this species to be of conservation concern in TX. � m/296
SPIRANTHES Rich. LADIES’-TRESSES, PEARL-TWIST
Roots fleshy, tuberous-thickened; stems unbranched, with few, mostly basal leaves or none persisting
until flowering time; flowers resupinate, in a slender, often twisted or spiraled spike;
perianth narrow, almost tubular, white to ivory, cream, or green, with or without green or
yellow markings; pollinia 2.
AA genus of 45 species of North America, South America, Eurasia, and Australia (Sheviak &
Brown 2002), but mainly n temperate. A number of species are cultivated as ornamentals.
While some species of Spiranthes are among the most common orchids in East TX, others are
very rare (e.g., S. parksii, S. brevilabris). Pollination in some is by long-tongued bees which
transfer pollinia attached to their tongues; other species reproduce via agamospermy (= the production
of seeds by asexual means) (Catling & Catling 1991b). The spiral arrangement of the
flowers is thought to be an adaptation to bee pollination, with the spiral functioning somewhat
like a ladder (Catling & Catling 1991b; Yatskievych 1999). The characteristic spiraling of the
inflorescence varies greatly, with inflorescences ranging from scarcely coiled to so tightly
coiled that the spiral aspect is lost (Sheviak 1982); in the key below, it is necessary to distinguish
“flowers single-ranked” from “flowers multi-ranked.” The term multi-ranked describes the situation
in which coiling is so tight that the flowers appear to be arranged in several vertical rows
or ranks in the inflorescence. For clear examples of flowers single-ranked, see the illustrations
of S. lacera var. gracilis, S. praecox, or S. tuberosa. For clear examples of flowers multi-ranked,
see the illustrations of S. cernua or S. magnicamporum. In the key and descriptions below, the
color of the perianth is usually described exclusive of the lip; lip color is usually described separately.
The common name LADIES’-TRESSES is derived from an old meaing of the word tress (a
braid) and refers to the braided appearance of the inflorescence; the derivation is through
Latin, tricia, plait, which comes from Greek, tricha, three-fold, in reference to the three strands
of plaits or braids (Durant 1976). (Greek: speira, a coil or spiral, and anthos, flower, from the spiraled
inflorescence)
REFERENCES: Correll 1947; Catling & McIntosh 1979; Garay 1980; Catling 1981, 1982, 1983a,
1983b; Sheviak 1982, 1991; MacRoberts et al. 1997; Brown 1999, 2001; Sheviak & Brown 2002.
1. Axis of inflorescence glabrous or essentially so (as seen under magnification); leaves (if present
at flowering time) all basal.
2. Perianth 5.5–11 mm long; leaves (if present) mostly 5 mm or less wide, erect or ascending,
without a petiole, the lower portion sheathing the stem, linear to narrowly lanceolate or oblong-elliptic.
3. Lip tapering from broad base to narrow obtuse apex, yellowish or yellowish green, not
marked or veined with green; inflorescence often 1-sided (rarely slightly spiraled); leaves
usually withering and dried by flowering time; plants flowering Nov–Dec ______________ S. longilabris