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BRASSICACEAE

MUSTARD FAMILY

Reed C. Rollins, except as specified

Annual to subshrub
Leaves generally basal and cauline, alternate, generally simple; stipules 0
Inflorescence: generally raceme
Flower bisexual; sepals 4, free; petals (0)4, free, generally white or yellow, often clawed; stamens generally (2,4)6, generally 4 long, 2 short; ovary 1, superior, chambers generally 2, septum membranous, connecting 2 parietal placentas, style 1, stigma simple or 2-lobed
Fruit: generally capsule ("silique") with 2 deciduous valves, sometimes breaking transversely or indehiscent
Seeds 1–many per chamber
Genera in family: 300+ genera, 3000+ species: worldwide, especially cool regions; some cultivated for food (especially Brassica, Raphanus ) and ornamental
Recent taxonomic note: Recently treated to include Capparaceae [Rodman et al. 1993 Ann Missouri Bot Gard 80:686–699; Rollins 1993 Cruciferae of Continental North America. Stanford Univ Press]
Family description, key to genera by Robert A. Price.

ARABIS

ROCK CRESS

Biennial, perennial herb; base woody or not; hairs 0 to dense, simple, forked, stellate, or multibranched; caudex branched or not
Stem branched or not, cylindric, leafy
Leaves: basal petioled, entire or dentate; cauline generally sessile, entire or dentate, base often lobed, often clasping stem
Inflorescence: bracts 0
Flower erect to reflexed; sepals erect; petals spoon-shaped to oblong and narrowed at base or narrowly obovate, white to deep purple, rarely straw-colored
Fruit erect to reflexed, linear, straight to curved, flat parallel to septum, rarely ± cylindric
Seeds ± many, generally 1 row per chamber, flat or plump, winged or not; embryonic root at edges of both cotyledons
Species in genus: ± 120 species: temp North America, Eurasia, Africa
Etymology: (Latin: of Arabia)

Native

A. hirsuta (L.) Scop.

Biennial, weak per; caudex branched or not; hairs simple or forked, coarse, spreading
Stems 1–several, simple or branched above, erect, 2–7 dm
Leaves: basal short-petioled, 2–8 cm, oblong to obovate, entire to dentate, tip obtuse; cauline sessile, 1–5(7) cm, lanceolate to obovate, sagittate, clasping stem
Fruit 3–6 cm, flat, glabrous; pedicel 0.5–1.5 cm; hairs 0, rarely sparse; style 0.5–1 mm
Seed ± round to ± rectangular; wing prominent or narrow on 1 end to 0
Ecology: Gravelly soils, swales, disturbed sites
Elevation: 1000–2600 m.
Bioregional distribution: Klamath Ranges, Outer North Coast Ranges, Cascade Range, Sierra Nevada, San Bernardino Mountains, White and Inyo Mountains
Distribution outside California: to Alaska, e Canada, Colorado
Var. eschscholtziana (Andrz.) Rollins OR to AK, e Asia; var. hirsuta native of Eur, Asia, not in North America.

Native

var. pycnocarpa (M. Hopkins) Rollins


Stem: hairs ± throughout
Leaves: basal hairy; cauline generally overlapped, lower ± hairy
Flower: outer sepals weakly sac-like at base; petals < 5(–8) mm, white to cream-white
Fruit erect
Chromosomes: 2n=16,32
Ecology: Meadows, gravel bars, shady slopes, moist, disturbed sites
Elevation: 1000–1900 m.
Bioregional distribution: Cascade Range, Sierra Nevada, San Bernardino Mountains, White and Inyo Mountains
Distribution outside California: to Alaska, e Canada
Synonyms: A. p. M. Hopkins

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