Plants annual or biennial, never bulbiferous. Stems prostrate or decumbent, 1-30 cm, freely rooting at nodes, forming mats. Leaves opposite, sessile; blade oblanceolate to rhombic, 2-20 × 0.5-10 mm. Inflorescences leafy. Flowers 1-8, slightly bilateral; sepals 1-1.5 mm; petals 5, connate proximally, white, unequal, 1-2 mm; stamens 3, anther pink or yellow. Seeds 0.7-1.2 mm, tuberculate; elaiosome present. 2n = 20, 40.

Flowering spring. Pools, springs, meadows, other wet or moist places; 0-3700 m; Greenland; St. Pierre and Miquelon; B.C., Man., N.B., Nfld. and Labr., N.S., Nunavut, N.W.T., Ont., P.E.I., Que., Yukon; Alaska, Calif., Idaho, Maine, Mass., Mont., Nev., N.H., N.Y., Oreg., Utah, Vt., Wash., Wyo.; Central America; South America; Europe; Asia; Africa; Arctic regions.

Montia fontana displays a multitude of forms varying in stature, leaf shape, and seed size. Segregate species, varieties, and subspecies have been named. Based on my study of worldwide collections of the species, much variation in M. fontana is attributable to phenotypic differentiation of ramets produced by local environmental conditions and unrelated to genetic variation. Until macromolecular or other studies shed light on the variation in M. fontana, it seems pointless to recognize infraspecific taxa or segregate species.

Lax, branching annual or seldom perennial, 1-3 dm, often rooting from the nodes; lvs oblanceolate or spatulate or obovate, 0.5-1.3 cm; pedicels solitary or paired in the axils and terminal, to 1 cm, or the fls in 2-4-fld cymules from the upper axils; pet 5, white, ca 1.5 mm, often unequal, united at the base into a short tube split on one side; stamens 3. Springs, brooks, or wet soil, often ±aquatic; irregularly cosmopolitan, with 4 vars. differing in the ornamentation of the seed- coat. June-Sept. Our plants, with the seed-coat shiny and nearly smooth, belong to the chiefly boreal var. fontana, occurring s. to N.S. and Me. (M. lamprosperma; M. rivularis, a ±perennial phase)

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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