Arabis holboellii, Holboell rockcress

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Intermountain Flora
Biennial (or perrenial), 2.5-7 (10) dm tall, with 1 or occasionally few stems, from a simple crown; herbage densely pubescent with branched hairs, sometimes mixed with coarser simple or forked hairs, especially on the lower stem, sometimes glabrous above; stem(s) stout, erect, simple or, in robust or injured plants, branched; basal leaves more or less rosulate, 1.5-4 (5.5) cm long, 2-6 (8.5) mm wide, spatulate to oblanceolate, tapering to a winged petiole, obtuse or actue apically, entire or springly dentate; cauline leaves many, often overlapping, oblong-lanceolate, sometimes narrowly so, sessile, auriculate or sagittate, acute apically, revolute-margined; raceme elongating in fruit; sepals 3-5 mm long, oblong, rounded to obtuse, greenish-yellow to purplish, sparsely pubescent, scarious-margined; petals 5-8 mm long, oblanceolate, sometimes narrowly so, pale lavender to purple, rarely white; fruiting pedicels abruptly bent downward at the base to divaricately descending (curved downward), (6) 7-18 mm long; siliques strictly reflexed against the rachis to divaricately descending, straight to slightly curved, 4.5-6.5 (7.5) cm long, 1.5-2 mm wide, glabrous, the valves 1-nerved to or beyond midlength; stigma subsessile; seeds in 1 row in each locule, 1.3-1.6 mm long, suborbicular, narrowly winged distally or all around, the cotyledons accumbent; 2n = 14, 18, 21, 22, 28, 42.

Cronquist, A., Holmgren, N.H., and Holmgren, P.K. (2005) "Intermountain Flora" pg. 364, vol. 2 part B, The New York Botanical Garden New York.