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Aristida
See list of 7 species in this genusWhen measuring the length of the lemma, be sure to include the basal callus in the measurement. Reference: Allred (2003).
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1a. Lemma awns twisted together at the base forming a spiral column 8–15 mm tall [Fig. 191]; callus of lemma 3–4 mm long
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1b. Lemma awns not twisted together into a column (though they may be coiled at the base independent of one another) [Figs. 189,190]; callus of lemma 0.3–2 mm long
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2a. Lower glume with 3–7 veins; awns subequal, (12–) 35–65 (–70) mm long
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2b. Lower glume with 1 or 2 veins; awns subequal or distinctly unequal, 1–27 (–30) mm long
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4a. Central awn 10–15 mm long; lateral awns 5–10 mm long, usually somewhat divergent from near the base
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4b. Central awn 3–8 mm long; lateral awns 1–4 mm long, straight and erect
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3b. Central awn not coiled at base [Fig. 190]
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5a. Plants annual; lateral awns of lemma usually markedly reduced in length compared with the central awn, up to 66% as long as the central awn
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5b. Plants perennial; lateral awns of lemma equal or subequal in length to the central awn [Fig. 190]
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6a. Lower glume 4–7 mm long, usually less than 75% as long as the upper glume; lemmas 7–13 mm long, with a callus 0.5–1.8 mm long
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6b. Lower glume 5–10 mm long, more than 75% as long as the upper glume (and sometimes even exceeding the length of the upper glume); lemmas 4–8 mm long, with a callus 0.4–0.8 mm long
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Each photo represents one species in this genus.