Alyssum alyssoides, alyssum

Image Source -

Intermountain Flora
Annual; herbage grayish-green with appressed-stellate hairs; stems 0.8-2 (3) dm tall, simple to much-branched from the base or near the base; leaves 0.5-2.5 cm long, 1.5-4.5 mm wide, oblanceolate, often narrowly so, narrowed to a sessile base, obtuse to acute apically; raceme with appressed-stellate pubescence, the axis elongating in fruit; sepals (2) 2.3-3.4 mm long, persistent in fruit; petals pale, yellow. aging cream, or white, 2.5-4 mm long, narrowly oblanceolate to linear, entire and rounded to emarginate; fruiting pedicels divergent, 2-3 mm long; silicles with appressed-stellate pubescence, broadly ovate to orbicular, 3-3.7 mm long and about as wide, emarginate, inflated with flat margins; mature style (0.2) 0.3-0.5 mm long; seeds (1) 2 per locule, 1.2-1.5 mm long, obovoid or broadly ovoid, plump, yellowish-brown, minutely tuberculate, winged all around, the wing 0.1 mm wide, the cotyledons accumbent; 2n = 32.

Cronquist, A., Holmgren, N.H., and Holmgren, P.K. (2005) "Intermountain Flora" pg. 278, vol. 2 part B, The New York Botanical Garden New York.