1. Leavenworthia torulosa A. Gray (necklace gladecress)

Map 1358

Plants annual. Stems absent. Leaves in a basal rosette, (2–)3–8(–9) cm long, petiolate, the leaf blades oblanceolate in outline, pinnately divided with 12–18 lateral lobes and 1 considerably larger, terminal lobe, these toothed or lobed. Inflorescences of single, long-stalked flowers arising from the rosette leaves. Sepals 3.5–5.5 mm long, nearly erect, oblong, greenish or lavender. Petals 6–10 mm long, 3.5–6.0 mm wide, deeply notched at the tip, white, lavender, or yellow. Styles 2.5–5.0 mm long. Fruits somewhat fleshy, erect, 1.5–3.0 cm long, 5–8 times as long as wide, linear, somewhat flattened parallel to the septum, constricted along the replum between the seeds. Seeds in 1 row in each locule, 2.5–3.5 mm in diameter, circular in outline, flattened, the margin nearly wingless, the surface with a netlike or honeycomb-like pattern of ridges and pits, dark brown. 2n=30. March–April.

Uncommon, known thus far only from St. Louis County (Kentucky, Tennessee, Missouri). Habitat unknown but probably limestone or dolomite glades.

A single historical specimen at the Missouri Botanical Garden herbarium labeled as having been made by George Letterman at Allenton in 1882 consists of three plants of L. uniflora mounted on the same sheet with a single small specimen of L. torulosa. Lesquerella torulosa was once considered for listing under the federal Endangered Species Act because of its rarity and the perceived risk of extinction, but it subsequently was judged still to be too widespread in Kentucky and Tennessee to warrant listing. The plant labeled as having originated from Missouri represents a significant disjunction in the overall range of the species and perhaps was the result of some sort of mixup when the specimens were mounted.