Linum pratense
in N. L. Britton et al., N. Amer. Fl. 25: 69. 1907.
Herbs, annual, 5–60 cm, glabrous. Stems ± spreading or ascending, or branches from base prostrate. Leaves: blade linear to linear-oblanceolate, 8–20 × 0.7–2.3 mm. Inflorescences: open panicles or racemes. Pedicels 8–25 mm. Flowers homostylous; sepals ovate, 3–5 mm, margins glabrous, apex acute; petals usually blue, rarely white, obovate, 5–14 mm; stamens 3–5 mm; anthers 0.4–1.3 mm; staminodia present; styles distinct, 1–3 mm; stigmas capitate. Capsules broadly ovate to subglobose, 4–6 mm diam., apex obtuse, segments persistent on plant, margins ciliate. Seeds 3–5 × 1.2–1.6 mm. 2n = 18.
Phenology: Flowering Mar–Jun.
Habitat: Sandy prairies, roadsides, disturbed areas, limestone.
Elevation: 1200–2000 m.
Distribution
Ariz., Colo., Kans., N.Mex., Okla., Tex.
Discussion
In a study of pollination in Linum pratense, G. E. Uno (1984) observed that petals dropped soon after anthesis and the persistent sepals quickly moved inward, pressing the dehiscing anthers against the receptive stigmas. Small bees and flies were seen to visit flowers even after the petals fell. Uno noted sepals closing in both L. lewisii and L. rigidum, but in these species the stamens tend to be somewhat shorter than the styles so self-pollination was less likely.
C. M. Rogers (1984) wrote that some plants of Linum pratense intergrade with L. lewisii in areas where their ranges overlap; however, in most of its range, L. pratense is the only blue-flowered Linum, and can be distinguished from the occasional plant of L. bienne or L. usitatissimum by its lack of cilia on the inner sepals and its capitate stigmas.