Bull. Herb. Boissier, sér. 2, 7: 404. 1907.
Plants perennial, mat-forming. Taproots stout, woody. Stems suberect to ascending, green, 2–10-cm, retrorsely pubescent in lines, internodes of flowering-stems 2–7 times as long as leaves. Leaves tightly overlapping or not (vegetative and proximal cauline) or variably spaced (distal cauline), usually connate proximally, with tight, scarious to herbaceous sheath 0.5–1 mm; blade straight to outwardly curved, green, flat, obscurely 1-veined abaxially, oblong or spatulate to elliptic, 5–10 × 0.7–2 mm, flexuous, margins not thickened, scarious, rarely ciliate proximally, apex green or purple, rounded, flat to navicular, shiny, glabrous; axillary leaves mostly absent. Inflorescences 3–5-flowered, open cymes; bracts lanceolate, herbaceous. Pedicels 0.5–1 cm, usually densely stipitate-glandular. Flowers: hypanthium cupshaped; sepals 3-veined prominently in fruit, oblong to narrowly lanceolate (herbaceous portion often purple, oblong to narrowly oblanceolate), 3.5–4.5 mm, not enlarging in fruit, apex rarely purple, rounded, hooded (at least inner sepals) or not, glabrous to stipitate-glandular proximally; petals white or often lilac, broadly oblanceolate, 1.4–1.7 times as long as sepals, apex truncate, often shallowly notched. Capsules broadly ellipsoid, 5.5 mm, longer than sepals. Seeds brown, suborbiculate with radicle prolonged into beak, slightly compressed, 0.7–0.8 mm, smooth or obscurely scupltured (50×). 2n = 26.
Phenology: Flowering spring–summer.
Habitat: Dry, calcareous, gravelly to rocky slopes, fell-fields, snow beds, heath in low arctic to alpine areas
Elevation: 0-2500 m
Greenland, Alta., B.C., Nfld. and Labr. (Labr.), N.W.T., Nunavut, Que., Yukon, Alaska, circumpolar, Europe, Asia
Specimens labeled Arenaria sajanensis Willdenow ex Schlechtendal from western North America, although sometimes referred to M. biflora (e.g., H. J. Scoggan 1978–1979, part 3), are likely to be M. obtusiloba.
"-7timesaslongasleaves" is not declared as a valid unit of measurement for this property."-1.7timesaslongassepals" is not declared as a valid unit of measurement for this property.