Plants annual; viscid-aromatic, pilose, sometimes sparsely so, producing long, juvenile, floating basal leaves. Culms 3-35 cm, erect, ascending, or decumbent, sometimes becoming prostrate, not breaking apart at the nodes, usually branching only at the lower nodes. Leaves without ligules, sometimes with a "collar" line visible at the junction of the sheath and blade, especially when dry; blades flat or becoming involute in drying. Inflorescences terminal, clavate to capitate spikes, exserted at maturity, spikelets distichously arranged; disarticulation tardy, above the glumes and between the florets. Spikelets laterally compressed, with 4-40 florets. Glumes irregularly 2-5-toothed; lemmas deeply cleft and strongly 5-veined, veins terminating in prominent mucronate or awn-tipped teeth 1/3 - 1/2 or more as long as the lemma bodies, each tooth with an additional weaker vein on either side of a strong central vein, these extending about halfway to the base of the lemma; paleas well-developed, 2-veined; lodicules absent; anthers 3, white or pinkish, exserted on long, slender, ribbonlike filaments at anthesis; styles 2, apical, elongate, filiform, stigmatic for 1/3 – 1/2 of their length; stigmatic hairs short, often sparse. Caryopses slightly compressed laterally, oblong to elliptic; embryos 3/4 as long as to equaling the caryopses; epiblast absent, x = 10, probably.
Orcuttia is a genus of five species, all of which are restricted to vernal pools and similar habitats in California and northern Baja California, Mexico.
|1||Lemma teeth unequal, the central tooth the longest.||> 2|
|2||Lemmas 6-7 mm long, the teeth terminating in awns at least 1 mm long; caryopses 2.3-2.5 mm long||Orcuttia viscida|
|2||Lemmas 4-5 mm long, the teeth sharp-pointed or with awns to 0.5 mm long; caryopses 1.3-1.8 mm long.||> 3|
|3||Plants sparingly hairy; culms usually prostrate; spikes clavate||Orcuttia californica|
|3||Plants conspicuously hairy, grayish; culms erect or decumbent; spikes somewhat capitate||Orcuttia inaequalis|
|1||Lemma teeth essentially equal in length.||> 4|
|4||Culms usually prostrate; caryopses 1.5-1.8 mm long||Orcuttia californica|
|4||Culms erect, ascending, or decumbent; caryopses 2-3 mm long.||> 5|
|5||Culms 1-2 mm thick, branching only at the lower nodes; spikes congested, crowded towards the top; leaf blades 3-5 mm wide||Orcuttia pilosa|
|5||Culms 0.5-1 mm thick, often branching from the upper nodes; spikes not congested, even towards the top; leaf blades 1.5-2 mm wide||Orcuttia tenuis|