Richard Spellenberg

A new Oryzopsis from Idaho

A new species of ricegrass,Oryzopsis swallenii, from the sagebrush hills at the east end of the Lost River and Lemhi ranges in east central Idaho is described. The plant combines features ofStipa andOryzopsis, but is set apart fromStipa by virtue of a quickly deciduous awn and a blunt callus, and from other species inOryzopsis by its relatively long glumes and its chromosome number, 2n = 34. The chromosome number forO. exigua Thurb., 2n = 22, is also reported. A key is provided to separate this new species from others in the genus most similar to it.