Fuirena simplex var. aristulata
Sida 7: 336. 1978.
Herbs usually annual, rarely taller than 30–40 cm; rhizomes mostly absent, when present very short. Culms tufted (more slender than in preceding variety). Leaves: principal blades 5–12 cm. Spikelets to 12, lanceovoid or lanceoloid; fertile scales 2–3 mm. Flowers: anthers 1–3, 0.5–0.6 mm.
Phenology: Fruiting summer–fall.
Habitat: Sand or clay, silt, of prairie swales, alluvial terraces, moist waste sites, pond and lakeshores
Elevation: 0–500 m
Ark., Kans., La., Mo., Nebr., N.Mex., Okla., Tex.
Most North American material of var. simplex is cespitose, the rhizomes short. In such specimens the evident perennial habit and the longer anthers are more reliable characteristics.
"shortened" is not a number.