A small genus of annual herbs with narrow entire leaves. Flowers on long peduncles, yellow. Sepals 3. Petals 6. Stamens numerous, with dilated filaments. Carpels numerous, many-seeded, at first partially united, but free when mature. The name is from 1 Platystemon 39 broad, and 1 Platystemon 40 a stamen. Two species have been described; they are both dwarf hardy plants of straggling habit and no great merit.

1. P. Californicus. - Leaves and capsules hairy. Native of California, flowering in August.

2. P. leiocarpus. - Capsules smooth, flowers yellowish white. A native of Siberia.