Description

Key Characters:

Growth Form: Annual or sometimes biennial herbs, pubescent with simple hairs.

Stems: Stems ascending to erect, 2–5 dm long, usually branched above base, usually pubescent, the hairs spreading, occasionally glabrate.

Roots:

Leaves: Leaves simple. Alternate or rarely opposite. Basal leaves 4–6(–10) cm long. cauline leaves somewhat reduced, 1–3 cm long. Margins of basal leaves deeply serrate. cauline leaves serrate to subentire. Stipules absent.

Flowers: Flowers usually bractless in dense racemes 5–10 cm long, somewhat narrowed toward apex. Flowers bisexual (perfect), actinomorphic or rarely slightly irregular; white, pale yellow, or greenish, usually 2–3 mm long, sometimes absent. Calyx of 4 sepals, deciduous, erect, usually oblong, sometimes the inner 2 with gibbous bases that hold the nectar; ca. 0.5 mm long, caducous, margins white. Corolla of 4 petals, rarely absent, yellow, white, or lavender, entire to emarginate, rarely lobed or fimbriate, usually with an elongate claw; filiform, less than ca. 0.4 mm long, or absent. Stamens 2(4); anthers dithecal, opening by longitudinal slits. Ovary superior, 2(4?)-carpellate, usually 2-celled by means of a false, but usually complete septum, rarely 1-celled, sessile or rarely stipitate; ovules 1 to numerous, borne on parietal placentas on replum margin at periphery of ovary wall, campylotropous or occasionally anatropous; styles short or essentially absent; stigma capitate.

Fruit: Capsules divided into 2 cells by the usually thin and membranous septum; elongate (at least 3 times as long as wide) and referred to as a silique; flattened at right angles to the septum; broadly obovate to suborbicular; usually 2–2.5 mm long; the apical notch narrow; prominent; the margins clearly exceeding the style. Seeds 1 to numerous; often becoming mucilaginous when wet; endosperm essentially absent; 1–1.3 mm long.

Ploidy: 2n = 32

Habitat: Known only from disturbed sites on northern; leeward Hawai‘i.

Elevation Range: