Annual, patulous glandular-pubescent, 5-10 cm. Stems many, branching from base. Branches filiform. Leaves 0.8-1.5 x 0.2 cm., linear, mostly 7-nerved. Flowers arranged in dichasial cymes. Pedicels shorter than calyx, erect in fruit. Calyx 6 mm. or more, campanulate; sepals unequal, lanceolate-acuminate, white-margined, 3-5-nerved. Petals one third as long as calyx, white, ovate-oblong. Capsule shorter than calyx, oblong. Seeds finely tuberculate. Fl. April.