Difference between revisions of "Achnatherum contractum"

(B.L. Johnson) Barkworth
Common names: Contracted ricegrass
Synonyms: Oryzopsis contracta
Treatment appears in FNA Volume 24. Treatment on page 141.
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|synonyms={{Treatment/ID/Synonym
 
|synonyms={{Treatment/ID/Synonym
 
|name=Oryzopsis contracta
 
|name=Oryzopsis contracta
|authority=unknown
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|authority=
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|rank=species
 
}}
 
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|hierarchy=Poaceae;Poaceae subfam. Pooideae;Poaceae tribe Stipeae;Achnatherum;Achnatherum contractum
 
|hierarchy=Poaceae;Poaceae subfam. Pooideae;Poaceae tribe Stipeae;Achnatherum;Achnatherum contractum
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|distribution=Mont.;Colo.;Wyo.
 
|distribution=Mont.;Colo.;Wyo.
|discussion=<p>Achnatherum contractum grows in rocky grasslands in eastern Idaho, southwestern Montana, and Wyoming. It is a fertile derivative of a Piptatherum micranthum x Achnatherum hymenoides hybrid (Shechter and Johnson 1968; Shechter 1969). Immature specimens of A. hymenoides are sometimes confused with A. contractum because they have contracted panicles with appressed branches and pedicels; they differ in having pedicel pairs in which the shorter pedicel is more than half as long as the longer pedicel.</p>
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|discussion=<p><i>Achnatherum contractum</i> grows in rocky grasslands in eastern Idaho, southwestern Montana, and Wyoming. It is a fertile derivative of a <i>Piptatherum micranthum</i> x <i>Achnatherum hymenoides</i> hybrid (Shechter and Johnson 1968; Shechter 1969). Immature specimens of <i>A. hymenoides</i> are sometimes confused with <i>A. contractum</i> because they have contracted panicles with appressed branches and pedicels; they differ in having pedicel pairs in which the shorter pedicel is more than half as long as the longer pedicel.</p>
 
|tables=
 
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-->{{#Taxon:
 
name=Achnatherum contractum
 
name=Achnatherum contractum
|author=
 
 
|authority=(B.L. Johnson) Barkworth
 
|authority=(B.L. Johnson) Barkworth
 
|rank=species
 
|rank=species
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|family=Poaceae
 
|family=Poaceae
 
|illustrator=Cindy Roché
 
|illustrator=Cindy Roché
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|illustration copyright=Utah State University
 
|distribution=Mont.;Colo.;Wyo.
 
|distribution=Mont.;Colo.;Wyo.
 
|reference=None
 
|reference=None
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|special status=
 
|special status=
|source xml=https://bibilujan@bitbucket.org/aafc-mbb/fna-data-curation.git/src/314eb390f968962f596ae85f506b4b3db8683b1b/coarse_grained_fna_xml/V24/V24_189.xml
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|source xml=https://bitbucket.org/aafc-mbb/fna-data-curation/src/200273ad09963decb8fc72550212de541d86569d/coarse_grained_fna_xml/V24/V24_189.xml
 
|subfamily=Poaceae subfam. Pooideae
 
|subfamily=Poaceae subfam. Pooideae
 
|tribe=Poaceae tribe Stipeae
 
|tribe=Poaceae tribe Stipeae

Latest revision as of 16:22, 11 May 2021

Please click on the illustration for a higher resolution version.
Illustrator: Cindy Roché

Copyright: Utah State University

Plants tightly cespitose, not rhizomatous. Culms 30-50 cm tall, 1-1.3 mm thick, glabrous; nodes 3-4. Sheaths glabrous; collars puberulent, hairs about 0.2 mm, sometimes the margins with poorly developed tufts of hair to 0.5 mm; ligules 1.8-5 mm, broadly to narrowly acute, glabrous; blades 0.5-1.5 mm wide, flat or convolute, abaxial surfaces smooth, adaxial surfaces scabridulous. Panicles 6-25 cm long, 7-15 cm wide; branches ascending to strongly divergent, longest branches 5-8 cm; pedicels appressed to the branches, paired, unequal, shorter pedicels in each pair usually less than 1/2 as long as the longer pedicels. Spikelets confined to the distal 1/2 of the branches. Glumes saccate below, tapering at midlength, glabrous, midveins sometimes scabridulous, apices acuminate; lower glumes 5.5-7 mm long, 0.9-1.5 mm wide; upper glumes about 0.3 mm shorter; florets 2.5-3.5 mm long, 0.7-1.5 mm thick, fusiform to obovoid; calluses 0.3-0.5 mm, blunt; lemmas densely pilose, hairs at midlength and on the apices similar, 1.2-2 mm, apical lobes 0.5-0.6 mm; awns 6.5-9 mm, readily deciduous, scabrous; paleas similar to the lemmas in length, texture, and pubescence, distal hairs exceeding the paleal apices, apices rounded, flat; anthers about 1.5 mm, penicillate, dehiscent, well-filled. Caryopses 1.5-2.5 mm, globose to obovoid. 2n = 48.

Discussion

Achnatherum contractum grows in rocky grasslands in eastern Idaho, southwestern Montana, and Wyoming. It is a fertile derivative of a Piptatherum micranthum x Achnatherum hymenoides hybrid (Shechter and Johnson 1968; Shechter 1969). Immature specimens of A. hymenoides are sometimes confused with A. contractum because they have contracted panicles with appressed branches and pedicels; they differ in having pedicel pairs in which the shorter pedicel is more than half as long as the longer pedicel.

Selected References

None.

Lower Taxa

None.