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1 Flowers borne in heads (glomerules) of 2 or more, individual flowers not subtended by two bracteoles (in addition to the bracteole at the base of the pedicel); [subgenus Juncus, section Graminifolii]. |
2 Perianth 6-10 mm long; plant aquatic, submersed and sterile or emersed/stranded and fertile; stems weak, creeping, mat-forming |
2 Perianth < 6 mm long; plant of uplands or wetland margins, never submersed; stems erect, never creeping or mat-forming. |
3 Heads 1-5 (-10) per culm; [ calcareous glades inland, east to GA and TN] |
3 Heads >9 per culm; [collectively widespread]. |
4 Infructescence usually congested, (1.8-) 2.4-4.7 (-6.4) cm long; greatest distance between adjacent rhizome cataphylls (5.3-) 6.3-10.5 (-13.0) mm; rhizome width (measured between adjacent cataphylls) (0.8-) 1.0-1.4 (-1.9) mm |
4 Infructescence usually loose, (1.4-) 17.9-103.9 (-145) cm long; greatest distance between adjacent rhizome cataphylls (0.1-) 0.4-3.0 (-4.6) mm; rhizome width (measured between adjacent cataphylls) (0.4-) 1.0-3.5 (-4.5) mm. |
5 Widest leaf blade (2.6-) 3.1-4.5 (-7.0) mm wide; sheath of lowest leaf (3.2-) 4.3-7.8 (-9.7) cm long; tallest culm (27.2-) 50.8-81.2 (-100.7) cm; anthers (0.5-) 0.6-1.0 (-1.3) mm long, exserted; stem base (3.4-) 5.8-9.6 (-12.0) mm wide |
5 Widest leaf blade (1.3-) 1.6-2.6 (-3.5) mm wide; sheath of lowest leaf (1.7-) 2.2-3.8 (-4.7) cm long; tallest culm (19.2-) 26.0-44.0 (-56.8) cm; anthers (0.2-) 0.3-0.5 (-0.7) mm long, concealed by tepals; stem base (0.4-) 2.0-4.4 (-6.0) mm wide |
1 Flowers borne singly on branches of inflorescence, individual flowers subtended by two bracteoles (in addition to the bracteole at the base of the pedicel). |
6 Plants annual, without coarse roots or persistent leaf bases; [subgenus Agathryon, section Tenageia] |
7 Capsule apex acute to obtuse, usually shorter than or equaling inner tepals; inner tepals acute to subobtuse |
7 Capsule apex more or less truncate, usually exceeding inner tepals; inner tepals obtuse |
6 Plants perennial, with coarse roots or persistent leaf bases. |
 Show caption*© Thomas Gyselinck, some rights reserved (CC BY), uploaded by Thomas Gyselinck Auricles 3-6 mm long at summit of leaf sheath. |
9 Capsules < 3/4 length of perianth; unbranched terminal sections of the inflorescence with 2-5 flowers, the longest distance between the adjacent flowers (excluding the peduncle) 6-11 mm |
9 Capsules > 3/4 length of perianth; unbranched terminal sections of the inflorescence with 1-3 (-4) flowers, the longest distance between the adjacent flowers (excluding the peduncle) 0.5-5.5 mm |
8 Auricles < 2 mm long or absent. |
10 Cauline leaves present in addition to basal leaves; blades flat |
10 Cauline leaves absent. |
11 Leaf blades terete or channeled. |
12 Capsules 1- locular or pseudo-3- locular, widely elliptic to rounded, apex rounded; seeds 0.3-0.4 mm long |
12 Capsules 3- locular, elliptic, apex somewhat truncate; seeds 0.48-0.7 mm long |
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13 Perianth obtuse apically; capsule chestnut brown or darker; [ exotic, ranging south to MD] |
13 Perianth acute to acuminate; capsule light brown or tan; [native]. |
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15 Perianth usually 2.5-3.5 mm long; flowers secund; capsules globose to ellipsoid |
15 Perianth usually (3.3-) 4-5 (-5.7)mm long; flowers not secund; capsules ellipsoid or narrowly so |
16 Anthers 0.6-0.9 mm long; auricles scarious, to 0.5 mm long; [of c. US, marginally in the w. fringe of our area] |
16 Anthers 1.2-1.5 mm long; auricles scarious to membranous, 0.2-0.3 mm long; [of granitic flatrocks in the Piedmont from NC, SC, GA, and AL] |
14 Inflorescence bract longer than inflorescence; capsules 1- locular to falsely 3- locular. |
17 Auricles yellowish, glossy; perianth spreading in fruit |
17 Auricles whitish or straw colored, dull; perianth not spreading. |
18 Mature capsules pale brown or darker; [of the Coastal Plain] |
18 Mature capsules pale tan or darker; [of prairies and plains, east to KY, se TN] |
