|John R. Reeder|
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. Named for Charles
Russell Orcutt (1864-1929), a California botanist.
Orcuttia is a genus of five species, all of which are endemic to vernal pools and similar habitats in California and northern Baja California, Mexico. The aquatic leaves of most species of Orcuttia do not exhibit Kranz leaf anatomy even though, like the aerial and floating leaves, their carbon isotype ratios indicate that they employ C4 photosynthesis (Boykin et al. 2008).
SELECTED REFERENCE Boykin, L.M., W.T Pockman, and T.K. Lowrey. 2008. Leaf anatomy of Orcuttieae (Poaceae: Chloridoideae): more evidence of C4 photosynthesis withou Kranz anatomy. Madrono 55: 143- 150.
Lemma teeth unequal, the central tooth the longest (2)
Lemma teeth essentially equal in length (4)
Lemmas 6-7 mm long, the teeth terminating in awns at least 1 mm long; caryopses 2.3-2.5 mm long ..... 1. O. viscida
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)
Plants sparingly hairy; culms usually prostrate; spikes clavate ..... 2. O. californica
Plants conspicuously hairy, grayish; culms erect or decumbent; spikes somewhat capitate ..... 3. O. inaequalis
Culms usually prostrate; caryopses 1.5-1.8 mm long ..... 2. O. californica
Culms erect, ascending, or decumbent; caryopses 2-3 mm long (5)
Culms 1-2 mm thick, branching only at the lower nodes; spikes congested, crowded towards the top; leaf blades 3-5 mm wide ..... 4. O. pilosa
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 ..... 5. O. tenuis
1. Orcuttia viscida (Hoover) Reeder
Plants pilose, very viscid, strongly aromatic. Culms 3-10(15) cm, simple, erect, often spreading in age. Leaves usually without a "collar" line; blades 2-4 mm wide. Spikes 3-5 cm, somewhat congested (less so than those of O. inaequalis); lower and upper internodes 3-7 mm. Spikelets with 6-20(30) florets. Glumes subequal, 5-6 mm, unequally 3-toothed, teeth as long as the bodies, awn-tipped; lemmas 6-7 mm, teeth as long as the lemma bodies, central tooth evidently the longest, awns at least 1 mm; paleas at least 3/4 as long as the lemmas; anthers about 2 mm. Caryopses 2.3-2.5 mm, broadly elliptical; embryos about as long as the caryopses. 2n = 28.
Orcuttia viscida grows at elevations below 120 m in Sacramento County, California. Its awn-tipped lemma teeth curve outward at maturity, giving the spikes a distinctive, bristly appearance. It is listed as an endangered species by the U.S. Fish and Wildlife Service.
2. Orcuttia californica Vasey
Plants sparsely hairy. Culms 5-15(20) cm, simple, sometimes geniculate, usually prostrate and forming mats. Leaves with a faint "collar" line usually evident when dry; blades 1-2 cm long, 2-3 mm wide. Spikes 3-6 cm; lower internodes 5-10 mm; upper internodes about 1 mm. Spikelets with 5-15(25) florets. Glumes subequal or the lower glumes a little shorter than the upper, 2-3(4) mm, irregularly toothed; lemmas about 5 mm, teeth equal or the central tooth a little longer than the others, awns to 0.5 mm; paleas about equal to the lemmas; anthers about 2 mm. Caryopses 1.5-1.8 mm, narrowly elliptical; embryos at least 3/4 as long as the caryopses. 2n = 32.
Orcuttia californica grows at elevations below 625 m in Los Angeles, Riverside, and San Diego counties, California and northern Baja California Norte, Mexico. It is listed as an endangered species by the U.S. Fish and Wildlife Service.
3. Orcuttia inaequalis Hoover
San Joaquin Orcuttgrass
Plants cespitose, conspicuously hairy, grayish. Culms 5-15(25) cm, usually ascending to erect, occasionally spreading and forming mats. Leaves usually without a "collar" line; blades 1-4 cm long, 2-4 mm wide. Spikes 2-3.5(5) cm, more or less capitate, usually densely congested; lower and upper internodes 1-4 mm. Spikelets with 4-20(30) florets. Glumes subequal, about 3 mm, irregularly toothed; lemmas 4-5 mm, teeth about 1/2 as long as the lemma, central tooth conspicuously longer than the others, teeth sharp, if awn-tipped, awns less than 0.5 mm; paleas about equal to the lemmas; anthers about 2 mm. Caryopses 1.3-1.5 mm, broadly elliptical; embryos about as long as the caryopses. 2n = 24.
Orcuttia inaequalis grows at elevations below 575 m in Fresno, Madera, Merced, Stanislaus, and Tulare counties, California. It is listed as a threatened species by the U.S. Fish and Wildlife Service.
4. Orcuttia pilosa Hoover
Plants cespitose, hairy, usually densely so. Culms 5-20(35) cm tall, 1-2 mm thick, simple or branching at the lower nodes, erect or decumbent, sometimes geniculate. Leaves with a faint "collar" line usually evident when dry; blades 4-6 cm long, 3-5(8) mm wide. Spikes to 10 cm; lower internodes 5-15 mm; upper internodes 1.5-3 mm. Spikelets with 10-40 florets. Glumes about 3 mm, irregularly 3-toothed; lemmas 4-5 mm, teeth about equal and 1/3-1/2 as long as the lemmas, acute or awn-tipped; anthers 2.5-3 mm. Caryopses about 2 mm, elliptical; embryos 3/4 or more as long as the caryopses. 2n = 30.
Orcuttia pilosa grows at elevations below 150 m in Madera, Merced, Stanislaus, and Tehama counties, California. It is listed as an endangered species by the U.S. Fish and Wildlife Service.
5. Orcuttia tenuis Hitchc.
Plants sometimes weakly cespitose, but often with a single main culm branching 2-10 cm above the base, sparsely hairy. Culms 5-15(25) cm tall, 0.5-1 mm thick, often strictly erect, but sometimes decumbent when "top heavy" from profuse branching above. Leaves usually without a "collar" line; blades 1-3 cm long, 1.5-2 mm wide. Spikes 5-10 cm, more congested distally than basally; lower internodes 5-15 mm; upper internodes 2-7 mm. Spikelets with 5-20 florets. Glumes subequal or the lower glumes a little shorter than the upper, 3-6 mm, with 3-5 teeth to 1 mm; lemmas 4.5-6 mm, acute or awn-tipped teeth about equal and 1/2 as long as the lemma, spreading or slightly recurved; paleas slightly shorter than the lemmas; anthers about 3 mm. Caryopses about 3 mm, narrowly oblong; embryos nearly as long as the caryopses. 2n = 26.
Orcuttia tenuis grows at elevations between 25-100 m in Shasta and Tehama counties of the Central Valley of California, with outlying populations in Sacramento County and the lower montane regions of Lake, Shasta, and Siskiyou counties, California. It is listed as a threatened species by the U.S. Fish and Wildlife Service.