22. Cerastium semidecandrum Linnaeus, Sp. Pl. 1: 438. 1753.
Five-stamen mouse-ear chickweed
Plants annual, with slender taproot. Stems erect or ascending, branching at base, 1-20 cm, viscid, covered with short, dense, glandular and eglandular hairs; short axillary tufts of leaves absent. Leaves not marcescent, sessile but proximal leaves often spatulate; blade 5-18 × 2-5 mm, covered with short, white hairs; basal leaves with blade narrowly oblanceolate and ± spatulate, apex obtuse; cauline with blades ovate to elliptic-oblong, apex obtuse to acute. Inflorescences open, 3-30-flowered cymes; bracts lanceolate, with broad, scarious margins, glandular-pubescent. Pedicels curved at apex, often sharply angled at base, 3-8(-12) mm, 1-3 times as long as capsule, densely glandular-pubescent and viscid. Flowers: sepals narrowly lanceolate, 3-5 mm, margins broad, apex acute, glandular-pubescent; petals with unbranched veins, oblanceolate, 2-3 mm, shorter than sepals, apex notched; stamens 5; styles 5. Capsules cylindric, slightly curved, 4.5-6.5 mm, 1.5-2 times as long as sepals; teeth 10, erect, margins convolute. Seeds pale yellowish brown, 0.4-0.6 mm, finely tuberculate; testa not inflated. 2n = 36.
Flowering spring. Common weed in dry, sandy, and gravelly places, roadsides and footpaths, parking lots, dunes; 0-300 m; introduced; B.C., N.S., Ont.; Ark., Conn., Fla., Ga., Idaho, Ill., Ind., Kans., La., Md., Mass., Mich., Mo., Nebr., N.J., N.Y., N.C., Ohio, Oreg., Pa., R.I., S.C., Wash., Wis.; Eurasia.
The very broad, scarious margins of the sepals and bracts distinguish this small, ephemeral species.