PLANT: Annual, 5-20 cm tall, simple or with 1-5 dichotomous branches, glabrous.

LEAVES: mostly simple, sometimes with 3 lobes, 1-3.5 cm long, glabrous.

INFLORESCENCE: open, the flowers 1-2, axillary and terminal.

FLOWERS: mostly sessile; calyx glabrous, narrowly campanulate, 9-15 mm long, the lobes equalling the tube, the hyaline membranes usually wider than the herbaceous ribs; corolla nocturnal in AZ, closed during the day, funnelform, 12-20-(25) mm long, white to cream, the lobe margins often tinged purplish; stamens inserted on the lower tube; filaments swollen and short pubescent at the base; style included. 2n=18.

NOTES: 2 vars. from CA to NV.