Achnatherum aridum

(M.E. Jones) Barkworth
Common names: Mormon needlegrass
Endemic
Synonyms: Stipa arida
Treatment appears in FNA Volume 24. Treatment on page 131.
Please click on the illustration for a higher resolution version.
Illustrator: Cindy Roché

Copyright: Utah State University

Plants cespitose, not rhizomatous. Culms 35-85 cm tall, 0.9-2.5 mm thick, usually glabrous and smooth, sometimes scabridulous or puberulent; nodes 2-3. Basal sheaths glabrous, upper sheath margins hyaline distally; collars of the basal sheaths occasionally with a small tuft of 0.8 mm hair on the sides, collars of the upper leaves glabrous, scabridulous, or sparsely puberulent; ligules 0.2-1.5 mm, truncate to rounded, erose, sometimes ciliate, cilia about 0.05 mm; blades 0.9-3 mm wide, abaxial surfaces smooth or scabridulous, glabrous, adaxial surfaces hirtellous, hairs to 0.5 mm. Panicles 5-17 cm long, 1-1.5 cm wide, contracted, bases often enclosed at anthesis; branches appressed or strongly ascending, straight, lower branches 1.5-4 cm. Lower glumes 8-15 mm long, 0.6-0.8 mm wide; upper glumes 1-5 mm shorter; florets 4-6.5 mm long, 0.6-1.1 mm thick, fusiform, terete; calluses 0.2-1 mm, sharp; lemmas evenly hairy on the lower portion, hairs 0.2-0.5 mm, the distal 1/5 – 1/4 often glabrous, apical hairs absent or fewer than 5, to 1.5 mm; awns 40-80 mm, persistent, obscurely once-geniculate, scabridulous, terminal segment flexuous; paleas 2-3.2 mm, 1/2 - 3/4 as long as the lemmas, pubescent, hairs exceeding the apices, apices rounded, flat; anthers 2-3.5 mm, dehiscent, not penicillate. 2n = unknown.

Distribution

Colo., N.Mex., Tex., Utah, Calif., Ariz., Nev.

Discussion

Achnatherum aridum grows on rocky outcrops, in shrub-steppe and pinyon-juniper associations, from southeastern California to Colorado and New Mexico, at 1200-2000 m. It has also been reported from Texas, but no specimens documenting these reports have been located. It has not been found in Mexico.

Selected References

None.

Lower Taxa

None.

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

... more about "Achnatherum aridum"
scabridulous +  and smooth +
membranous +  and scarious +
not penicillate +
0.2 cm2 mm <br />0.002 m <br /> (0.35 cm3.5 mm <br />0.0035 m <br />) +
awned +, bifid +, bilobed +  and entire +
0 cm0 mm <br />0 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
Mary E. Barkworth +
(M.E. Jones) Barkworth +
1 (?) +  and 3 (?) +
flexuous +
subterminal +  and eccentric +
scabridulous +
once-geniculate +
4 cm40 mm <br />0.04 m <br /> (8 cm80 mm <br />0.08 m <br />) +
keeled +  and rounded +
pseudopetiolate +  and branching +
swelling +
not evident +
involute +, convolute +  and flat +
0.9mm;3mm +
ascending;appressed +
spikelike +
well-developed +
0.02 cm0.2 mm <br />2.0e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (?) +
puberulent +  and glabrous +
Mormon needlegrass +
branching +  and not branching +
perennial +  and annual +
35 cm350 mm <br />0.35 m <br /> (85 cm850 mm <br />0.85 m <br />) +
intravaginal +  and basal +
puberulent +  and glabrous +
10 cm100 mm <br />0.1 m <br /> (250 cm2,500 mm <br />2.5 m <br />) +
not woody +
0.09 cm0.9 mm <br />9.0e-4 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
Colo. +, N.Mex. +, Tex. +, Utah +, Calif. +, Ariz. +  and Nev. +
1/5 +  and 1/3 +
liquid +, soft +  and hard +
capillary +
pistillate +  and staminate +
0.4 cm4 mm <br />0.004 m <br /> (0.65 cm6.5 mm <br />0.0065 m <br />) +
sometimes longer +
terete +  and fusiform +
1-10-veined +
subtending +
obtuse +, acute +  and acuminate +
membranous +
divergent +  and distributed +
1/5 +  and 1/4 +
uncinate +
0.02 cm0.2 mm <br />2.0e-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 +
truncate +  and rounded +
0.02 cm0.2 mm <br />2.0e-4 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
membranous +
membranous +
inconspicuous +
not lobed +
1.5 cm15 mm <br />0.015 m <br /> (4 cm40 mm <br />0.04 m <br />) +
0.8 cm8 mm <br />0.008 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
0.6mm +  and 0.8mm +
concealed +  and prominent +
2 +  and 3 +
2 +  and 1 +
pubescent +  and glabrous +
well-developed +
1/2 +  and 3/4 +
not keeled +
reduced +
0.2 cm2 mm <br />0.002 m <br /> (0.32 cm3.2 mm <br />0.0032 m <br />) +
5cm +  and 17cm +
1 cm10 mm <br />0.01 m <br /> (1.5 cm15 mm <br />0.015 m <br />) +
dry +  and fleshy +
not prolonged +
1 +  and 60 +
unisexual +  and bisexual +
laterally compressed +  and terete +
1 (?) +  and 3 (?) +
simple +  and compound +
Stipa arida +
Achnatherum aridum +
Achnatherum +
species +
membranous +
0.1 cm1 mm <br />0.001 m <br /> (0.5 cm5 mm <br />0.005 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 +