Achnatherum arnowiae

(S.L. Welsh & N.D Atwood) Barkworth
Common names: Arnow's ricegrass
Treatment appears in FNA Volume 24. Treatment on page 141.
Please click on the illustration for a higher resolution version.
Illustrator: Cindy Roché

Copyright: Utah State University

Plants tightly cespitose, not rhizomatous. Culms 15-75 cm tall. Sheaths smooth, mostly glabrous, margins ciliate; collars glabrous, with or without tufts of hair at the sides, hairs 0.7-2 mm; ligules 1-4 mm, glabrous or sparsely hairy, acute, sometimes ciliate; blades 1-2 mm wide, involute, 0.5-1 mm in diameter, abaxial surfaces scabridulous or smooth, adaxial surfaces densely hairy, hairs about 0.2 mm. Panicles 5-20 cm long, 0.5-2.8 cm wide, loosely contracted; branches strongly ascending, longest branches 0.5-2.5 (5) cm. Spikelets evenly distributed along the branches; pedicels loosely appressed to the branches, paired, unequal, shorter pedicels in each pair usually less than 1/2 as long as the longer pedicels. Glumes slightly unequal, saccate below, tapering from about midlength, veins and sometimes also the intercostal regions puberulent, hairs to 0.1 mm, apices acute to acuminate; lower glumes 5.1-6.1 mm; upper glumes 4.3-5.2 mm; florets 2.8-4.2 mm, ovoid; calluses 0.2-0.4 mm, acute; lemmas indurate, dark gray-brown, smooth, densely pilose, hairs at midlength and at the apices similar, 2-3 mm, easily rubbed off, apices not lobed; awns 3-4.4 mm, rapidly deciduous, not geniculate, scabrous; paleas similar to the lemmas in length and texture, glabrous, apices pinched; anthers about 1 mm, dehiscent, penicillate. Caryopses 1-1.7 mm long, 0.8-1 mm in diameter, globose to obovoid. 2n = unknown.

Discussion

Achnatherum arnowiae grows in pinyon-juniper, sagebrush, and mixed desert shrub communities in Utah, at 1400-2000 m. Welsh and Atwood (2003) state that specimens belonging to A. arnowiae are often filed as A. xbloomeri, and they suggest that this species may also be hybrid in origin, possibly with Hesperostipa comata as one of its parents. Another possibility is that it is a derivative of A. hymenoides that is adapted to particular soil types.

Selected References

None.

Lower Taxa

None.

"decumbent" is not a number."prolonged" is not a number."prolonged" is not a number.

... more about "Achnatherum arnowiae"
smooth +  and scabridulous +
membranous +  and scarious +
penicillate +
1 cm10 mm <br />0.01 m <br /> (?) +
awned +, bifid +, bilobed +  and entire +
Acute (?) +  and Acuminate (?) +
0 cm0 mm <br />0 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
Mary E. Barkworth +
(S.L. Welsh & N.D Atwood) Barkworth +
1 (?) +  and 3 (?) +
flexuous +
subterminal +  and eccentric +
usually scabrous +  and scabridulous +
not geniculate +
0.3 cm3 mm <br />0.003 m <br /> (0.44 cm4.4 mm <br />0.0044 m <br />) +
keeled +  and rounded +
pseudopetiolate +  and branching +
intravaginal +, extravaginal +, branching +  and basal +
swelling +
not evident +
involute +, convolute +  and flat +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
1mm;2mm +
flexuous +  and straight +
spikelike +
well-developed +
0.02 cm0.2 mm <br />2.0e-4 m <br /> (0.04 cm0.4 mm <br />4.0e-4 m <br />) +
Arnow's ricegrass +
branching +  and not branching +
perennial +  and annual +
15 cm150 mm <br />0.15 m <br /> (75 cm750 mm <br />0.75 m <br />) +
intravaginal +  and basal +
10 cm100 mm <br />0.1 m <br /> (250 cm2,500 mm <br />2.5 m <br />) +
not woody +
Mont. +, Oreg. +, Ariz. +, Idaho +, Wash. +, S.Dak. +, Tex. +, Calif. +, Colo. +, Wyo. +, Utah +, N.Mex. +, Nev. +, Nebr. +, Alaska +, Kans. +, N.Dak. +, Okla. +, Alta. +, B.C. +, Man. +, Sask. +, Yukon +, Ark. +  and Minn. +
1/5 +  and 1/3 +
liquid +, soft +  and hard +
capillary +
pistillate +  and staminate +
sometimes longer +
2.8mm +  and 4.2mm +
1-10-veined +
subtending +
tapering +
unequal +
membranous +
divergent +  and distributed +
0.2 cm2 mm <br />0.002 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
solid +  and hollow +
basally concentrated +  and evenly distributed +
0 cm0 mm <br />0 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
dark gray-brown +
ovate +, rectangular +  and lanceolate +
hairy +  and glabrous +
0.1 cm1 mm <br />0.001 m <br /> (0.4 cm4 mm <br />0.004 m <br />) +
membranous +
membranous +
inconspicuous +
not lobed +
0.5 cm5 mm <br />0.005 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
0.51 cm5.1 mm <br />0.0051 m <br /> (0.61 cm6.1 mm <br />0.0061 m <br />) +
concealed +  and prominent +
2 +  and 1 +
pubescent +  and glabrous +
0 (?) +  and 1/2 (?) +
well-developed +
not keeled +
reduced +
5cm +  and 20cm +
0.5 cm5 mm <br />0.005 m <br /> (2.8 cm28 mm <br />0.028 m <br />) +
dry +  and fleshy +
not prolonged +
1 +  and 60 +
unisexual +  and bisexual +
laterally compressed +  and terete +
1 (?) +  and 3 (?) +
simple +  and compound +
Gramineae +
Achnatherum arnowiae +
Achnatherum +
species +
membranous +
0.43 cm4.3 mm <br />0.0043 m <br /> (0.52 cm5.2 mm <br />0.0052 m <br />) +
inconspicuous +
0.1 cm1 mm <br />0.001 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
plant +  and cespitose +
aquatic +  and terrestrial +