Arabis divaricarpa
Purple Rock Cress

Flower Top

Valeport Wildlife Management Area

Note the four petals, four long stamens, and two short stamens.  These features are characteristic of the Cruciferae family.

Divaricarpa: Answers to key questions in Budd's Flora and Manual of Montana Vascular Plants leading to this species. 

plants 20-80 cm high; NOT [plants 10-20 cm high]

caudex usually simple or few-branched, not woody; NOT [caudex usually branched and woody]

stems arising from terminal bud of the rosette; NOT [outer stems decumbent-based, arising from lateral buds, basal leaves erect]

most stems > 1mm wide; NOT [stems <= 1 mm wide in the middle]

pubescence of lower stems sparse and 2- to 3-branched; NOT [pubescence of lower stems more branched]

NOT [basal leaves often blunt-tipped, felt-like with dense branched hairs]

cauline leaves auriculate; NOT [cauline leaves without auricles]

cauline leaves not rolled; NOT [margins of cauline leaves rolled under]

cauline leaves not whitish-hairy; NOT [cauline leaves whitish with dense hair]

at least some siliques spreading; NOT [all siliques erect or ascending], NOT [all siliques sharply reflexed and pendulous]

siliques 5-10 cm long; NOT [siliques 1-5 cm long]

siliques 1-2 mm wide, often > 1.5 mm wide; NOT [siliques 1.5-3.5 mm wide], NOT [siliques always <= 1.5 mm wide]


Arabis: Answers to key questions in Budd's Flora and Manual of Montana Vascular Plants leading to this genus. 

basal leaves entire to shallowly dentate; NOT [basal leaves deeply lobed or divided into leaflets]

plants with pubescence mostly or entirely of branched hairs; NOT [plants glabrous, or the pubescence of simple hairs]

flowers much smaller; NOT [flowers 20-25 mm across]

silique not samara-like

siliques linear to oblong, > 5 times as long as wide

siliques flattened parallel to the septum; NOT [siliques flattened at right angles to septum]; NOT [siliques round or 4-angled in cross section]

silique beakless, often with a short style at the tip <= 1 mm long; NOT [silique with a large, usually seedless (sometimes 1-seeded), beak-like, upper portion and a seed-bearing lower portion]

central partition entire; NOT [central partition with an opening sometimes almost reduced to the margin]

silique with more than one seed; NOT [silique 1-seeded]


Cruciferae: Answers to key questions in Budd's Flora  leading to this family. 

herbs; NOT [shrubs or trees]

plants terrestrial or semiaquatic; NOT [plants aquatic, leaves submerged or floating]

plants not with colored milky juice

plants with more than one normal leaf

some or all leaves alternate; NOT [leaves opposite, whorled, or basal]

leaves without stipules, or having glands; NOT [leaves with stipules]

flowers with two floral rings

calyx regular; NOT [calyx irregular, some sepals smaller than others]

sepals 4

corolla regular in shape; NOT [corolla irregular in shape]

each petal distinct from the others

petals 4

stamens 6, four long and two short

ovary superior; NOT [ovary inferior]

carpels 1 or 2