Plants perennial; clumped, rhizomes woody. Culms 10-60 cm, branched above the base. Leaves mostly basal; auricles absent; ligules of hairs; blades flat, strongly veined, sharply pointed. Inflorescencesterminal, usually exceeding the upper leaves, contracted panicles; branches ascending to erect. Spikelets laterally compressed, unawned, with 3-7 bisexual florets, distal florets reduced; disarticulation beneath the caryopses. Glumes subequal, longer than the adjacent lemmas but exceeded by the distal florets, acuminate; lower glumes 5-7-veined; upper glumes 7-11-veined; calluses hairy; lemmas membranous to papery, 5-7-veined, densely villous on the margins, sometimes also between the veins, unawned to mucronate; paleas equaling or exceeding the lemmas; anthers 3. Caryopses falling free from the lemma and palea. x = 10. Named for Jason Richard Swallen (1903-1991), a U.S. Department of Agriculture botanist and a former head of the Department of Botany at the Smithsonian Institution.

Swallenia is a monotypic genus, endemic to California. It is unusual in that only its caryopses break off the plant.

1.   Swallenia alexandrae (Swallen) Soderstr. & H.F. Decker
Eureka-Valley Dunegrass

Culms 10-40(60) cm, stiff, erect; nodes villous. Sheaths villous on the upper margins; blades 5-14 cm long, 3-8 mm wide. Panicles 4-10 cm; branches to 35 mm, with 1-3 spikelets. Spikelets 10-15 mm, persistent. Glumes 9-14 mm; lemmas 7-9 mm. Caryopses about 4 mm long, about 2 mm in diameter. 2n = 20.

Swallenia alexandrae grows on sand dunes in Inyo County, California. It is only known from four sites, all between 900-1200 m, in the Eureka Valley of northern Inyo County. At these sites, it forms dense colonies 1-2 m across. It is state-listed as rare and federally-listed as endangered because of off-road vehicle activity.