Ann. Sci. Nat. (Paris) 25: 18, plate 4. 1832.
Herbs glabrous or sparsely and minutely glandular distally. Stems erect, unbranched or spreading and branched near base, secondary branches few or none, branching not dichotomous, 5–20(–30) cm. Leaves little reduced distally, crowded and often exceeding subtending internode, 10–25 × 1–3 mm; petiole 0–10 mm; blade very narrowly elliptic or lanceolate to sublinear. Inflorescences with flowers arising as proximally as first 1–3 nodes from base. Flowers: sepals 0.6–1.3 mm, reflexed singly; petals 0.8–1.5mm; pollen 90–100% fertile; stigma subglobose, surrounded by anthers at anthesis. Capsules ascending, flattened, 8–17 × 1–2 mm, not constricted between seeds, valve margins entire or minutely undulate, 2 valves remaining attached to septum after dehiscence, septum straight; pedicel 0–0.5 mm. Seeds 24–50, all developing, arranged obliquely to septum and subopposite seeds in adjacent locule, forming 2 even rows in capsule, light brown, 0.7–1.1 × 0.3–0.4 mm, glabrous. 2n = 14.
Phenology: Flowering May–Sep.
Habitat: Drying margins of meadows, streams, lakes and pools.
Elevation: 800–3000 m.
Calif., Idaho, Mont., Nev., Oreg., Wash., Wyo., South America (Argentina, Chile).
Gayophytum humile is most similar to the allotetraploid G. racemosum and, on the basis of morphology, may be one of its parents. The two species are most distinct in their mature capsules; in G. humile the two lateral valves remain attached to the septum at dehiscence, whereas in G. racemosum all four valves separate from the septum at dehiscence.