| 1. Lemma teeth unequal, central tooth generally longest |
| |
| 2. Lemma 67 mm, teeth awned, awns > 1 mm; fruit ± 2.5 mm |
| O. viscida |
| 2' Lemma < 5 mm, teeth sharp-pointed or awned, awns < 0.5 mm; fruit < 2 mm |
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| 3. Plant sparsely hairy; stem generally prostrate; inflorescence with spikelets well separated on axis below, crowded toward tip; Southwestern California |
| O. californica |
| 3' Plant conspicuously hairy, grayish; stem erect or ± decumbent; spikelets crowded, inflorescence ± head-like; San Joaquin Valley |
| O. inaequalis |
| |
| 4. Stem generally prostrate; fruit 1.52 mm |
| O. californica |
| 4' Stem erect, ascending, or decumbent; fruit 2.53 mm |
| |
| 5. Stem branching only at lower nodes; inflorescence with upper spikelets densely crowded, lower well separated; plant generally densely hairy |
| O. pilosa |
| 5' Stem ± slender, often branching from upper nodes; spikelets evenly spaced, not densely crowded; plant sparsely hairy |
| O. tenuis
|