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Jepson Interchange (more information)
©Copyright 1993 by the Regents of the University of California
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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. X divaricarpa A. Nelson

Biennial, rarely per; caudex branched or not; hairs branched, appressed, generally 3–5-rayed
Stems 1–3, simple or branched above, 3–9 dm; hairs 0 or below
Leaves: basal 2–6 cm, widely oblanceolate to narrowly spoon-shaped, dentate to subentire, hairs sparse, tip ± acute; cauline sessile, narrowly oblong to lanceolate, often sagittate, clasping stem, entire or lower ± dentate, hairs 0 or sparse
Flower: petals spoon-shaped, pink to purplish
Fruit ascending to spreading, rarely ± reflexed, 2–8 cm, straight; pedicel ascending to ± reflexed, 6–12 mm; style very short or 0
Seed ± round; wing narrow
Chromosomes: 2n=14,13+2,21,20+2,28
Ecology: Gravelly, calcareous soils
Elevation: 2100–3300 m.
Bioregional distribution: Cascade Range, Sierra Nevada, Great Basin Floristic Province
Distribution outside California: to Rocky Mtns, e Canada
Flowering time: Jul–Aug
Synonyms: var. interposita (Greene) Rollins
(see Rollins 1983 Amer J Bot 70:625–634 for discussion of hybridity)

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bioregional map for ARABIS%20&mathx;divaricarpa being generated
 
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