Family: Poaceae
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Robert J. Soreng Plants perennial; usually densely tufted, rarely mod-erately densely tufted, usually neither rhizomatous nor stolon-iferous, infrequently short-rhizomatous or stoloniferous, rarely with distinct rhizomes. Basal branching intravaginal or intra- and extravaginal. Culms 10–60(70) cm tall, 0.5–1.8 mm thick, erect or the bases decumbent, terete or weakly compressed; nodesterete, 0–2 exserted. Sheaths closed for 1/4–3/4 their length, terete, smooth or scabrous, glabrous, bases of basal sheaths glabrous, distal sheath lengths 1.6–10 times blade lengths; collars smooth or scabrous, glabrous; ligules of cauline leaves 1–3(6) mm, smooth or scabrous, truncate to acute, ligules of the innovation leaves 0.2–0.5(2.5) mm, scabrous, usually truncate; innovation blades sometimes distinctly different from the cauline blades, 0.5–2 mm wide, involute, moderately thick, moderately firm, adaxial surfaces usually densely scabrous or hispidulous to softly puberulent, infrequently nearly smooth and glabrous; cauline bladessubequal or the midcauline blades longest or the blades gradually reduced in length distally, 0.5–3 mm wide, flat, folded, or involute, usually thin, usually withering, abaxial surfaces smooth or scabrous, apices narrowly to broadly prow-shaped, flag leaf blades 0.5–5(6) cm. Panicles 2–10(12) cm, usually erect, contracted or loosely contracted, narrowly lanceoloid to ovoid, congested or moderately congested, with 10–100 spikelets and 1–3(5) branches per node; branches 0.5–4(5) cm, erect or steeply ascending, fairly straight, slender to stout, terete to angled, smooth or scabrous, with 1–15 spikelets. Spikelets (3)4–10 mm, lengths to 3 times widths, broadly lanceolate to narrowly ovate, laterally compressed, not sexually dimorphic; florets 2–6; rachilla internodes 0.5–1.2 mm, smooth or scabrous. Glumes lanceolate, distinctly keeled; lower glumes 3-veined, distinctly shorter than the lowest lemmas; calluses glabrous or diffusely webbed, hairs less than 1/4 the lemma length; lemmas (3)4–7 mm, lanceolate to broadly lanceolate, distinctly keeled, membranous to thinly membranous, smooth or sparsely to densely scabrous, glabrous or the keels and/or marginal veins puberulent proximally, lateral veins obscure to prominent, margins glabrous, apices acute; palea keelsscabrous, intercostal regions glabrous; anthers vestigial (0.1–0.2 mm), aborted late in development, or 2–3.5 mm. 2n = 28, 28+II, 56, 56+II, 59, ca. 70. Poa cusickii grows in rich meadows in sagebrush scrub to rocky alpine slopes, from the southwestern Yukon Territory to Manitoba and North Dakota, south to central California and eastern Colorado. It is gynodioecious or dioecious. |