1. Valerianella Mill. (corn salad, lamb’s lettuce)
Plants annual or
less commonly biennial. Stems usually dichotomously forked several times,
angled, glabrous or sparsely and inconspicuously hairy along the angles. Basal
leaves sessile or short-petiolate, the blades simple, spatulate to obovate,
mostly rounded at the tip, the margins mostly entire, grading into the stem
leaves; stem leaves mostly sessile, often with the bases fused around the stem,
oblong-spatulate to lanceolate, rounded to bluntly pointed at the tip, the
margins entire or few-toothed near the base, glabrous or more commonly
inconspicuously hairy along the margins and the midvein of the undersurface.
Stipules absent. Inflorescences dense small headlike clusters, these solitary
or more commonly paired at the branch tips, with small lanceolate to narrowly
elliptic or narrowly spatulate bracts surrounding each cluster. Flowers mostly
perfect, epigynous, each subtended by a small bractlet. Calyces absent or
reduced to a minute crown. Corollas actinomorphic or slightly zygomorphic,
5-lobed, trumpet-shaped to narrowly bell-shaped, the tube often inconspicuously
pouched at the base. Stamens 3, the filaments attached near the top of the
corolla tube, the anthers attached at their midpoint, white. Pistils 1 per
flower, apparently of 3 carpels. Ovary inferior, with 3 locules, but only 1 of
these fertile, with 1 ovule, the others empty. Style 1, the stigma usually
slightly 3-lobed. Fruits achenelike, usually straw-colored at maturity, the
fertile locule becoming leathery and indehiscent, the sterile locules
persistent and differentiated in shape and size from the fertile one. About 60
species, North America, Europe, Asia.
Species of Valerianella
are classified principally on the basis of fruit morphology, thus some
specimens lacking fruits can be difficult to determine with confidence.
However, crossing experiments have shown that distinctive fruit morphologies
within some species complexes are actually the result of minor genetic
variations (see below for more discussion). The vernacular names “corn salad”
and “lamb’s lettuce” refer to the use of young plants of several species in the
genus as potherbs and salad greens.