10. Arabidopsis thaliana (Linnaeus) Heynhold in Holl & Heynhold,. Fl. Sachsen 1: 538. 1842; Arabis thaliana Linnaeus, Sp. Pl. 2: 665. 1753; Conringia thaliana (Linnaeus) Reichenbach, Fl. Germ. Excurs. Il. 686. 1826; Crucifera thaliana (Linnaeus) E. H. L. Krause in Sturm, Fl. Deutschland, ed. 2, 6: 86. 1902; Erysimum thalianum (Linnaeus) Kittel, Taschenb. Fl. Deutschl. ed. 2, 899. 1844; Hesperis thaliana (Linnaeus) Kuntze, Rev. Gen. Pl. 2: 935. 1891; Pilosella thaliana (Linnaeus) Kosteletzky, Ind. Pl. Hort. Prag. 104. 1844; Sisymbrium thalianum (Linnaeus) J. Gay & Monnard, Ann. Sci. Nat. Bot., ser. 1, 7: 399. 1826; Stenophragma thalianum (Linnaeus) Celakovsky, Kvet. Ok. Prazs. 75. 1870. TYPE: “Hab. in Europae septentrionalis sabulosis.” Lectotype designated by anonymous [see Jarvis (2007: 308)], “Pilosella siliquata” in Thal, Sylv. Herc. 84, t. 7, f. D. 1588.
Cardamine pusilla A. Richard, Tent. Fl. Abyss. 1: 18. 1847; Arabidopsis thaliana var. pusilla (A. Richard) O. E. Schulz in Engler, Pflanzenr. IV. 105(Heft 86): 274. 1924; Sisymbrium thalianum (Linnaeus) Gay & Monnard var. pusillum (A. Richard) T. Durand & Schinz, Consp. Fl. Afr. 1(2): 99. 1898; Stenophragma thaliana (Linnaeus) Celakovsky var. pusilla (A. Richard) Engler, Hochgebirgsfl. Trop. Afr. 226. 1895. TYPE: Ethiopia, Begemdir, SchimperII.1311 (holotype, P; isotype, K).
Herbs, annual. Stems (2–)5–30(–60) cm, erect, 1 to many from the base, simple or branched above, basally pilose with predominantly simple trichomes, apically glabrous. Basal leaves shortly petiolate, rosulate; leaf blade obovate, spatulate, ovate, or elliptic, 0.8–3.5(–4.5) x (0.1–)0.2–1(–1.5) cm, adaxially with predominantly simple and stalked 2- or 3(or 4)-forked trichomes, margin entire, repand, serrulate, or dentate, apex obtuse; cauline leaves subsessile or sessile, usually few; blade lanceolate, linear, oblong, or elliptic, middle ones (0.4–)0.6–1.8(–2.5) x 0.1–0.6(–1) cm, margin entire or rarely sparsely dentate, apex acute to obtuse. Fruiting pedicels slender, divaricate, straight, 3–10(–15) mm. Sepals 1–2(–2.5) mm, glabrous or distally sparsely pubescent with simple trichomes, lateral pair not saccate; petals white, spatulate, 2–3.5(–4) x 0.5–1.5 mm, apex obtuse; claw short, not toothed; filaments white, 1.5–2 mm; ovules 40–70 per ovary. Fruits linear, terete, smooth, (0.8–)1–1.5(–2) cm x 0.5–0.8 mm; valves with a distinct midvein; style to 0.5 mm. Seeds ellipsoid, plump, light to reddish brown, 0.3–0.5 mm; cotyledons incumbent. 2n = 10.
Flowering: Jan–Jun(–Oct).
Habitat: sandy areas, roadsides, river banks, railroad tracks and embankments, open areas, disturbed habitats, pastures, grassy flats, fields, prairies, floodplains, woods, lawns, limestone ledges and crevices, bluffs, rocky slopes, cultivated ground, meadows, alkaline flats, shale and serpentine barrens, gravel, sandstone.
Elevation: 0–4250 m.
Distribution: Native range: all Europe (excluding Iceland) to central Asia; Africa (Algeria, Eritrea, Ethiopia, Kenya, Libya, Morocco, Tanzania, Tunisia, Uganda, Zaire), most of Asia (excluding Bahrain, Bangladesh, Bhutan, Cambodia, Iraq, Israel, Jordan, Kuwait, Kyrgyzstan, Laos, Malaysia, Myanmar, Nepal, New Guinea, Oman, Philippines, Qatar, Sri Lanka, Taiwan, Thailand, Turkmenistan, United Arab Emirates, Vietnam, Yemen). Introduced into: Argentina, Austalia, Canada (British Columbia, Ontario, Quebec), Chile, New Zealand, South Africa, United States (Alabama, Arkansas, California, Connecticut, Delaware, District of Columbia, Georgia, Idaho, Illinois, Indiana, Iowa, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Mississipi, Missouri, Montana, New Hampshire, New Jersey, New York, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Isand, South Carolina, Tennessee, Texas, Utah, Vermont, Virginia, Washingon, West Virginia); Uruguay.