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1 Inflorescence verticillate, typically with 10-16 panicle branches in 2-5 verticils (whorls) |
1 Inflorescence digitate, with 2-10 branches in a single verticil ( whorl) at the apex of the culm. |
2 Spikelets with 1 lower bisexual floret and 2 or more sterile/ staminate florets (these obviously differing from the single lower fertile floret). |
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3 Lemma apices not truncate, instead rounded to acute (sometimes the second sterile or staminate floret truncate, but not also the lower bisexual floret, as in C. barbata). |
4 Lowest lemmas ( bisexual) glabrous, not conspicuously pubescent on the margins (but midveins often scabrous), the lemma margins inrolled |
4 Lowest lemmas conspicuously pubescent on the margins (at least distally); lemma margins sometimes grooved but not conspicuously inrolled. |
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5 Second sterile floret not strongly inflated or only somewhat inflated apically. |
6 Spikelets tawny, strongly imbricate; [widespread non-native] |
6 Spikelets pale to dark grey, barely imbricate; [ waif, s. TX] |
2 Spikelets with 1 lower bisexual floret and 1 additional sterile or staminate floret. |
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8 Awns of the lemma diminuitive, 0.3-1.5 mm long, the lemma almost appearing mucronate. |
8 Awns of the lemma longer (and more apparent), 1.9- 37 mm long (sometimes the awn of the sterile or staminate floret reduced or smaller but the spikelets with at least some longer or well-developed awns). |
9 Lowest lemma margins and keels pubescent or pilose throughout. |
10 Plants perennial; lowest lemma 1.9-2.7 mm long, with appressed pubescence, the hairs < 1 mm long; [native, c. and s. TX southward] |
10 Plants annual; lowest lemma (2.3-) 2.5-4.2 mm long, the margins either appressed pubescent ( C. pilosa) or pilose with conspicuously longer distal hairs > 1.5 mm long ( C. virgata); [non-native, widespread or waif]. |
11 Panicles with 5-9 distinct branches; spikelets barely imbricate, pale to dark grey and often mottled when mature; lower lemma awns to 6 mm long; lower glumes 1.1-1.6 mm long; [ waif, s. TX] |
11 Panicles with 4-20 distinct branches, the spikelets strongly imbricate, not mottled; lower lemma awns 2.5-15 mm long; lower glumes 1.5-2.5 mm long; [non-native, widespread] |
9 Lowest lemma margins and keels glabrous or scabrous, sometimes with a few short hairs concentrated distally but not pubescent throughout. |
12 Lemma apices conspicuously bilobed (both the lower bisexual and upper staminate); spikelets pectinate, diverging at a wide angle from branch axes |
12 Lemma apices acute to obtuse, but not bilobed (or only the sterile or staminate lemma partly lobed); spikelets divergent, appressed, or otherwise. |
13 Panicles with 2-9 branches. |
14 Lowest lemmas linear to narrowly lanceolate, 2.9-4.0 mm long; sterile or staminate lemmas bilobed for a portion of their length; sheaths glabrous; culms to 50 cm |
14 Lowest lemmas elliptic to obovate, 2.0-5.4 mm long; sheaths glabrous, scabrous or somewhat pilose; culms to 100 cm |
13 Panicles with (5-) 8-15 branches. |
15 Plants annual; lower glumes 0.7-1.6 mm long; lowest lemmas 2.8-3.3 mm long; [FL] |
15 Plants perennial; lower glumes 2.7-3.0 mm long; lowest lemmas 3.7-4.3 mm long; [TX] |