1. Spiranthes cernua (L.) Rich. (common ladies’ tresses, nodding ladies’ tresses)
Pl. 117 e; Map 481
Flowering
stems 10–50 cm long, with sparse to dense, glandular hairs. Basal leaves 3 or
4, usually (but not always) absent at flowering time, 5–23 cm long, linear to
oblanceolate, glabrous. Flowers appearing as though in 2 or more ranks or
intertwined spirals along the flowering stems or sometimes no spirals
discernable. Sepals and lateral petals 6–11 mm long, white to light cream
colored, the lateral sepals free to the base or nearly so, only slightly
spreading, oriented parallel to the rest of the perianth. Lip 8–11 mm long,
ovate to oblong, sometimes somewhat constricted in the middle, the margins
entire or somewhat irregular toward the tip, white to light cream colored,
often tinged with yellow or greenish yellow in the middle of the inner surface.
Column 4 mm long, green. 2n=45, 60 (61, 62). August–November.
Scattered
nearly throughout Missouri, but most commonly south of the Missouri River
(eastern U.S. and adjacent Canada west to Nebraska and Texas). Glades, upland
prairies, and old fields on acidic substrates, also in acidic soils in mesic
forests, thickets, and open stream valleys. Rarely on floating mats in sinkhole
ponds.
The
origins of this polyploid species are still poorly understood. In Missouri, as elsewhere, it exists as several poorly defined races, which differ
inconsistently in such characters as lip shape and color, inflorescence
density, and whether or not basal leaves are present at flowering time.
Reproduction is accomplished by apogamy, with seeds containing multiple embryos
formed directly from unreduced ovule cells that do not complete meiosis
(Sheviak, 1982).