1. Myosotis macrosperma Engelm. (big-seeded scorpiongrass)

M. virginica var. macrosperma (Engelm.) Fernald

M. verna var. macrosperma (Engelm.) Chapm.

Map 1303, Pl. 309 a

Plants annual, with slender taproots. Stems 20–60 cm long, erect or ascending, not rooting at the lower nodes, solitary or occasionally few, usually unbranched below the inflorescence, moderately to densely pubescent with fine, loosely ascending to spreading, usually minutely pustular-based hairs, these not hooked at the tip. Leaf blades 2–8 cm long, 6–16 mm wide, lanceolate to narrowly oblong-elliptic or oblanceolate, rounded or angled to a bluntly or sharply pointed tip, the surfaces and margins densely pubescent with fine, loosely ascending to spreading, minutely pustular-based hairs, these not hooked at the tip. Inflorescences not paired, the spikelike racemes sometimes aggregated into few-branched panicles, the flowers with stalks 0.5–2.0 mm long at flowering, elongating to 2–4 mm at fruiting and loosely ascending (angled away from the axis) at fruiting with a noticeable bend or curve at the tip, the inflorescence with linear to narrowly oblong, leaflike bracts at the branch points and lowermost flowers. Calyces 1.5–2.5 mm long at flowering, elongating to 5–8 mm at fruiting, slightly zygomorphic at flowering but becoming nearly 2-lipped at fruiting, 5-lobed slightly less than (shorter teeth) to slightly more than (longer teeth) 1/2 of the way to the base, the 3 upper lobes shorter than the 2 lower lobes, especially at fruiting, triangular to narrowly triangular, densely pubescent with spreading, stiff hairs that are hooked at the tip. Corollas 2–3 mm long, broadly funnelform to trumpet-shaped, the tube 1.4–2.0 mm long, the spreading portion 1–2 mm in diameter (measured across the tips of the lobes), white or rarely pale blue. Stamens inserted below the midpoint of the corolla tube. Style 0.2–0.3 mm long, shorter than the nutlets. Nutlets 1.5–2.2 mm long, greenish brown to dark brown. April–June.

Scattered in the southeastern and southwestern portions of the state, uncommon north of the Missouri River (eastern U.S. west to Missouri and Texas; Canada). Bottomland prairies, upland prairies, bases and ledges of bluffs, swamps, bottomland forests, and mesic upland forests; also pastures, fallow fields, railroads, roadsides, and open, disturbed areas.

Some botanists have considered M. macrosperma a variety of the closely related M. verna (Steyermark, 1963), but Al-Shehbaz (1991) argued forcefully against this interpretation. In Missouri, it is the less common of the two and apparently is unable to colonize drier sites as efficiently as M. verna. Although the two taxa can be difficult to distinguish at flowering, the pubescence of the calyx appears to separate them reliably, as noted in the key to species above. At fruiting, M. macrosperma tends to be a more robust plant than is M. verna and has more open, elongated racemes (the fruits spaced 10–30 vs. 5–9 mm apart, as measured between the bases of adjacent stalks). The orientation of the stalks at fruiting also is a reliable character, but care must be taken not to misinterpret it in poorly pressed or immature specimens.