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Key to Juncus, KEY B: Subkey in Juncus

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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].
image of plant
Show caption*© Bruce A. Sorrie
..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.
............ ..8 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
image of plant
Show caption*© Alan Weakley
............ ..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
............ ........11 Leaf blades flat.
............ ............ 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].
............ ............ ..14 Inflorescence bract shorter than inflorescence; capsules 3-locular.
............ ............ ....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]
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