Achnatherum swallenii

(C.L. Hitchc. & Spellenb.) Barkworth
Common names: Swallen's needlegrass
Synonyms: Oryzopsis swallenii
Treatment appears in FNA Volume 24. Treatment on page 137.
Please click on the illustration for a higher resolution version.
Illustrator: Cindy Roché

Copyright: Utah State University

Plants tightly cespitose, not rhizomatous. Culms 15-25 cm tall, 0.5-1 mm thick, glabrous; nodes 2-3. Basal sheaths mostly glabrous, pubescent at the base, throats glabrous; collars, including the sides, glabrous; basal ligules 0.2-0.3 mm, obtuse to rounded, glabrous; upper ligules to 0.5 mm, rounded to broadly acute; blades 0.4-0.7 mm wide, arcuate, abaxial surfaces smooth or scabridulous, adaxial surfaces with hairs shorter than 0.5 mm. Panicles 3-6.5 cm long, 0.3-0.7 cm wide; branches appressed, lower branches 1-5 cm, with 1-5 spikelets. Glumes subequal, 4-5.5 mm, not saccate, apices narrowly acute to acuminate, midveins often prolonged into an awnlike tip; lower glumes 0.6-1 mm wide, apices narrowly acute; florets 2.5-3.5 mm long, 0.6-0.8 mm thick, fusiform, terete; calluses 0.1-0.2 mm, blunt; lemmas evenly hairy, hairs 0.3-0.5 mm, all similar in length, apical lobes 0.3-0.5 mm, thickly membranous; awns 5-6 mm, once-geniculate, readily deciduous, basal segment scabridulous; paleas 2.2-2.5 mm, slightly shorter than the lemmas; anthers 1.5-2 mm, dehiscent, not penicillate. Caryopses 2-3 mm, ovoid. 2n = 34.

Discussion

Achnatherum swallenii grows on open, rocky sites, frequently with low sagebrush, in Idaho and western Wyoming, at 1500-2200 m. It is a dominant species in parts of eastern Idaho, although it is poorly represented in collections.

Selected References

None.

Lower Taxa

None.

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

... more about "Achnatherum swallenii"
scabridulous +  and smooth +
membranous +  and scarious +
not penicillate +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
awned +, bifid +, bilobed +  and entire +
0 cm0 mm <br />0 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
Mary E. Barkworth +
(C.L. Hitchc. & Spellenb.) Barkworth +
1 (?) +  and 3 (?) +
flexuous +
subterminal +  and eccentric +
usually scabrous +  and scabridulous +
once-geniculate +
0.5 cm5 mm <br />0.005 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
keeled +  and rounded +
pubescent +  and glabrous +
pseudopetiolate +  and branching +
intravaginal +, extravaginal +, branching +  and basal +
swelling +
not evident +
involute +, convolute +  and flat +
0.4mm;0.7mm +
flexuous +  and straight +
spikelike +
well-developed +
0.01 cm0.1 mm <br />1.0e-4 m <br /> (0.02 cm0.2 mm <br />2.0e-4 m <br />) +
Swallen's needlegrass +
branching +  and not branching +
perennial +  and annual +
15 cm150 mm <br />0.15 m <br /> (25 cm250 mm <br />0.25 m <br />) +
intravaginal +  and basal +
10 cm100 mm <br />0.1 m <br /> (250 cm2,500 mm <br />2.5 m <br />) +
not woody +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
Idaho +  and Wyo. +
1/5 +  and 1/3 +
liquid +, soft +  and hard +
capillary +
pistillate +  and staminate +
0.25 cm2.5 mm <br />0.0025 m <br /> (0.35 cm3.5 mm <br />0.0035 m <br />) +
sometimes longer +
terete +  and fusiform +
1-10-veined +
subtending +
obtuse +, acute +  and acuminate +
subequal +
0.4 cm4 mm <br />0.004 m <br /> (0.55 cm5.5 mm <br />0.0055 m <br />) +
membranous +
divergent +  and distributed +
uncinate +
0.03 cm0.3 mm <br />3.0e-4 m <br /> (0.05 cm0.5 mm <br />5.0e-4 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 />) +
ovate +, rectangular +  and lanceolate +
stiffly membranous +  and coriaceous +
pubescent +  and glabrous +
membranous +
membranous +
inconspicuous +
not lobed +
1 cm10 mm <br />0.01 m <br /> (5 cm50 mm <br />0.05 m <br />) +
0.6mm +  and 1mm +
concealed +  and prominent +
2 +  and 3 +
2 +  and 1 +
pubescent +  and glabrous +
well-developed +
not keeled +
reduced +
0.22 cm2.2 mm <br />0.0022 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
3cm +  and 6.5cm +
0.3 cm3 mm <br />0.003 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
dry +  and fleshy +
not prolonged +
unisexual +  and bisexual +
laterally compressed +  and terete +
1 (?) +  and 3 (?) +
simple +  and compound +
Oryzopsis swallenii +
Achnatherum swallenii +
Achnatherum +
species +
awnlike +
membranous +
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 +