Plants perennial; cespitose, rhizomatous, rhizomes short, slender. Culms slender, often compressed. Sheaths usually keeled; ligules minute, membranous, often erose or ciliate; blades exhibiting Kranz anatomy, with few organelles in the external sheath and 5-7 isodiametric mesophyll cells between the vascular bundles. Inflorescences terminal, open to contracted panicles; primary branches few, slender; pedicels short, to 1 mm. Spikelets ellipsoid or lanceolate, initially somewhat compressed, ultimately expanding greatly. Glumes glabrous; lower glumes 1/3-1/2 as long as the spikelets, usually 3(5)-veined, acute; upper glumes and lower lemmas subequal, 3-5(7)-veined; lower florets sterile or staminate, often standing apart from the upper florets at maturity; lower paleas longer than the lower lemmas, greatly inflated at maturity, indurate; upper florets ovoid or ellipsoid; upper lemmas usually dull-colored, minutely papillose, papillae in longitudinal rows, apices acute. x = 9 or 10. Name from the Greek steinos, narrow, and chasma, yawning, presumably alluding to the gaping glumes and somewhat narrow spikelet when compared to Panicum (Clifford 1996).

Steinchisma is a genus of 5-6 species that grow in moist or wet, usually open, sandy areas in warm-temperate and tropical regions of the Western Hemisphere. A single species is native the Flora region. It is sometimes included in Panicum, but recent studies support its recognition as a separate genus. Photosynthesis in Steinchisma is intermediate between C₃ and C₄ plants.

1.   Steinchisma hians (Elliott) Nash
Gaping Panicgrass

Culms 20-75 cm, often compressed, at least basally, erect to decumbent, glabrous. Sheaths usually shorter than the internodes, terete or somewhat compressed, glabrous or sometimes sparsely hispid below the throat, margins scarious or sparsely ciliate at the summit; ligules 0.2-0.5 mm, membranous, erose-ciliate; blades 6-20 cm long, 2-5 mm wide, relatively long and slender, flat or folded, glabrous abaxially, mostly glabrous adaxially but sparsely pilose basally. Panicles 5-20 cm, about 1/2 as wide as long, delicate, open; primary branches flexible, spreading or drooping, with short, crowded secondary branches and pedicels. Spikelets 1.8-2.4 mm, often purplish, glabrous. Lower glumes acute; upper glumes and lower lemmas slightly exceeded by the enlarged, indurate, sterile paleas; upper florets 1.6-1.9 mm, dull-colored, minutely papillose, acute. 2n = 18, 20.

Steinchisma hians grows in moist or wet, usually open areas, and in moist pinelands, low woods, and ditches. Its range extends from the southeastern United States, through Mexico and Central America to Colombia, Brazil, and Argentina.