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).