10.10 ORYZOPSIS Michx.
Mary E. Barkworth

Plants perennial; cespitose, not rhizomatous. Culms 25–65 cm, erect or spreading, basal branching extravaginal; prophylls not visible; nodes glabrous. Leaves mostly basal; cleistogenes not developed; sheaths open, glabrous; auricles absent; ligules membranous, longest at the sides or rounded, ciliate; blades of basal leaves 30–90 cm, remaining green over winter, erect when young, recumbent in the fall, bases twisted, placing the abaxial surfaces uppermost, cauline leaf blades reduced, flag leaf blades 2–12 mm, conspicuously narrower than the top of the sheath. Inflorescences panicles, contracted. Spikelets 5–7.5 mm, with 1 floret; rachillas not prolonged beyond the base of the floret; disarticulation above the glumes, beneath the floret. Glumes subequal, 6–10-veined, apices mucronate; florets terete to laterally compressed; calluses usually less than 1/5 the length of the florets, blunt, distal portions pilose; lemmas coriaceous, pubescent at least basally, 3–5(9)-veined, margins strongly overlapping at maturity, awned, lemma-awn junction conspicuous, lobed, lobes 0.1–0.2 mm; awns more or less straight, deciduous; paleas similar to the lemmas in length, texture, and pubescence, concealed by the lemmas, 2-veined, flat between the veins; lodicules 2, free, membranous, 2-veined; anthers 3; styles 1, with 2 branches; ovaries glabrous. Caryopses falling with the lemma and palea. x = 11, 12. Name from the Greek oryza, ‘rice’, and opsis, ‘appearance’, in reference to a supposed resemblance to rice.

Oryzopsis is treated here as a monospecific genus that is restricted to North America. Hitchcock (1951) and Johnson (1945) treated it as including both Eurasian and North American taxa; Freitag (1975) and Tutin (1980) placed the Eurasian species in a separate genus, Piptatherum. Kam and Maze (1974) demonstrated that O. asperifolia differs from both North American and Eurasian species previously included in Oryzopsis in the development of its floret and callus, and in having 2-veined lodicules. Phylogenetic studies based on ITS sequence data have not yielded clear support for any particular treatment of Oryzopsis; they are consistent with the treatment presented here. The North American species previously included in Oryzopsis have been transferred to Achnatherum and Piptatherum.

SELECTED REFERENCES Dore, W.G. and J. McNeill. 1980. Grasses of Ontario. Research Branch, Agriculture Canada Monograph No. 26. Canadian Government Publishing Centre, Hull, Québec, Canada. 566 pp.; Freitag, H. 1975. The genus Piptatherum (Gramineae) in southwest Asia. Notes Roy. Bot. Gard. Edinburgh 33:341–408; Hitchcock, A.S. 1951. Manual of the Grasses of the United States, ed. 2, rev. A. Chase. U.S.D.A. Miscellaneous Publication No. 200. U.S. Government Printing Office, Washington, D.C., U.S.A. 1051 pp.; Jacobs, S.W.L., R. Bayer, J. Everett, M.O. Arriaga, M.E. Barkworth, A. Sabin-Badereau, M.A. Torres, F. Vázquez, and N. Bagnall. 2006. Systematics of the tribe Stipeae using molecular data. Aliso 23:349–361; Johnson, B.L. 1945. Cytotaxonomic studies in Oryzopsis. Bot. Gaz. 107:1–32; Kam, Y.K. and J. Maze. 1974. Studies on the relationships and evolution of supraspecific taxa utilizing developmental data: II. Relationships and evolution of Oryzopsis hymenoides, O. virescens, O. kingii, O. micrantha, and O. asperifolia. Bot. Gaz. 135:227–247; Tutin, T.G. 1980. Piptatherum Beauv. Pp. 246–247 in T.G. Tutin, V.H. Heywood, N.A. Burges, D.M. Moore, D.H. Valentine, S.M. Walters, and D.A. Webb (eds.). Flora Europaea, vol. 5. Cambridge University Press, Cambridge, England. 452 pp.




1. Oryzopsis asperifolia Michx. [p. 168]
Roughleaf Ricegrass, Winter Grass,
Oryzopsis à Feuilles Rudes
Culms 25–65 cm. Basal ligules 0.2–0.7 mm, rounded, some-times longest at the sides; blades of basal leaves 30–90 cm long, 4–9 mm wide, flag leaf blades 8–12 mm. Panicles 3.5–13 cm, contracted. Glumes subequal, 5–7.5 mm long, 2.5–4 mm wide, 6–10-veined, apices mucronate; florets 5–7 mm; calluses 0.8–2 mm, blunt, distal portions with a dense ruff of soft hairs; lemmas coriaceous or indurate at maturity, pale green, white, or yellowish, sometimes purple-tinged, glossy or dull, pubescent at least basally, margins overlapping, concealing the paleas; awns 7–15 mm; paleas similar to the lemmas; anthers 2–4 mm, usually penicillate. Caryopses 4–6.5 mm. 2n = 46.
Oryzopsis asperifolia grows in both deciduous and coniferous woods, generally on open, rocky ground in areas with well-developed duff. It is found from the Yukon and Northwest Territories south to New Mexico along the Rocky Mountains, and from British Columbia east to Newfoundland and Maryland. It is listed as endangered or threatened in Indiana, Ohio, New Jersey, Maryland, and Virginia.
Leaf development in Oryzopsis asperifolia is unusual in that the leaves start to develop in midsummer, the blades growing upright. As the year progresses, they bend over, but stay alive and green through winter and the following spring. The part of the sheaths that remains below the level of the duff is usually bright purple (Dore and McNeill 1980).