Alyssum

Annuals or perennials [biennials, subshrubs]; not scapose; trichomes sessile, stellate, with 2-6 minute basal branches (branches as many as 3-25), rays branched or not, sometimes trichomes simple [lepidote]. Stems erect, ascending, or decumbent, unbranched or branched. Leaves basal and cauline; petiolate or sessile; basal rosulate or not, petiolate or sessile, blade margins entire; cauline petiolate or sessile, blade (base cuneate or attenuate), margins entire. Racemes (few- to several-flowered, sometimes corymbose or paniculate). Fruiting pedicels ascending, divaricate, or reflexed, slender or stout. Flowers: sepals ovate or oblong, lateral pair not saccate; petals yellow or white [rarely pink], suborbicular, spatulate, oblanceolate, linear-oblanceolate, or, obovate (apex obtuse or emarginate); stamens tetradynamous; filaments not winged, uni- or bilaterally winged, appendaged, or toothed; anthers ovate or oblong; nectar glands (4), 1 on each side of lateral stamen, median glands absent; (placentation apical or parietal). Fruits sessile, ovate-oblong, obovate, or elliptic [obcordate, rarely globose], usually strongly flattened, latiseptate, rarely inflated; valves each not veined (smooth), pubescent or glabrous; replum (visible), rounded; septum complete, (membranous, translucent, veinless); ovules 1 or 2 [or 4-8] per ovary; stigma capitate. Seeds biseriate or aseriate, flattened, winged or not, orbicular or suborbicular to ovoid; seed coat (smooth or minutely reticulate), mucilaginous or not when wetted; cotyledons accumbent or incumbent.

Pet yellow, varying to white, gradually narrowed to the base; short filaments flanked by a single gland on each side; anthers short and blunt; ovary short, compressed; ovules 1-8 per locule; style slender but short; fr elliptic to orbicular, flattened parallel to the septum, each locule with a few seeds; herbs with entire or serrate lvs; ±pubescent with stellate hairs. 170, mainly Eurasia.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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