What plant is that?

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Photo Credit: © Francis R. Underwood 2012

The mystery plant for April is a small winter annual with a rosette of basal leaves.  The flowering stem, a scape, grows two to eight inches tall and has a raceme of white flowers.  The flowers have four petals, four sepals and six stamens.  The petals are deeply bifid or cleft and the four limbs of the petals form a cross which is the origin of the former family name of this plant.  The fruit, a silicle, is from ¼ to ¾  inches long. This plant is easily overlooked because of its small size. It grows along roadsides, fields and wasteplaces in dry sandy soil and blooms as early as February or even January when the winter has been mild.

It’s. . .