Annuals, to 25 cm. Stems erect or sprawling, branched distally, villous, especially distally. Leaves linear or subulate, 15-80 × 1.5-2(-4) mm, margins ± entire, faces moderately hairy. Involucres cylindric to narrowly obconic, 6-8.5 mm. Phyllaries 4, elliptic to oblong, hairy. Receptacles subulate, papillate, glabrous. Ray florets 4; (corollas yellow) laminae lance-elliptic, (0-)0.5-1 mm. Disc corolla lobes 4(-5). Anther appendages subulate (without wartlike glands; style apices lanceolate, glabrous). Cypselae black, ± linear, to 5 mm, hairy; pappi 0, or of 1-4 brown or white, linear to ovate or lanceolate, aristate scales (sometimes variable within heads). 2n = 24.

Flowering Mar-May. Shaded areas, woodlands, chaparral, deserts; 0-1000 m; Calif.

Because the rays are inconspicuous, plants of the self-pollinating Lasthenia microglossa are easy to overlook. Besides growing in habitats similar to those occupied by L. debilis, L. microglossa is found also beneath chaparral shrubs and extends into desert areas, where it grows near rocks that may provide favorable shade and moisture conditions.