Jepson Flora Project: Jepson Interchange    

 
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Jepson Interchange (more information)
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  • Up-to-date information about California vascular plants is available from the Jepson eFlora.

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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