(Linnaeus) Heynhold in F. Holl and G. Heynhold, Fl. Sachsen. 1: 538. 1842.
Linnaeus, Sp. Pl. 2: 665. 1753;
(Linnaeus) J. Gay & Monnard
; glabrous or pubescent, trichomes usually simple, sometimes mixed with stalked, forked ones.
simple or few from base, erect, unbranched or branched distally, (0.2-)0.5-3(-5) dm, pubescent basally, trichomes predominantly simple, glabrous apically.
shortly petiolate; blades obovate, spatulate, ovate, or elliptic, 0.8-3.5(-4.5) cm × (1-)2-10(-15) mm, margins entire, repand, or dentate, apex obtuse, adaxial surface with predominantly simple and stalked, 1-forked trichomes.
subsessile; blade lanceolate, linear, oblong, or elliptic, (0.4-)0.6-1.8(-2.5) cm × 1-6(-10) mm, margins usually entire, rarely toothed.
divaricate, 3-10(-15) mm.
sepals 1-2(-2.5) mm, lateral pair not saccate basally, (glabrous or sparsely pubescent distally, trichomes simple); petals white, spatulate, 2-3.5(-4) × 0.5-1.5 mm, (base attenuate to claw); filaments 1.5-2 mm.
cylindric or linear, smooth, terete, (0.8-) 1-1.5(-1.8) cm × 0.5-0.8 mm; valves each with distinct midvein; ovules 40-70 per ovary; style to 0.5 mm.
light brown, (plump), ellipsoid 0.3-0.5 mm; cotyledons incumbent.
Flowering Feb-May. Sandy areas along roadsides, stream banks, railroad tracks and embankments, open pastures, grassy flats, fields, prairies, floodplains, woods, lawns, limestone ledges and crevices, bluffs, shale and serpentine barrens, gravel, sandstone; 0-1000 m; introduced; B.C., Ont., Que.; Ala., Ark., Calif., Conn., Del., D.C., Ga., Idaho, Ill., Ind., Iowa, Ky., La., Maine, Md., Mass., Mich., Miss., Mo., Mont., N.H., N.J., N.Y., NC., Ohio, Okla., Oreg., Pa., R.I., S.C., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis.; Europe; sw, c Asia; introduced also nearly worldwide.
is the most widely used model organism in plant biology. Its small genome size, fully sequenced in the year 2000, chromosome number, fast growth cycle (from seed germination to set in four to six weeks), small size (hundreds can be grown in a pot and thousands in a growth chamber), autogamous breeding system (induced mutations are expressed in two generations), and ability to grow on various synthetic media, all make the species an ideal system in experimental biology.