1 |
Aerial stems lasting more than one year; main stem often unbranched; stomata sunken, in one row; strobili mucronate apically; sheath teeth membranous, deciduous, light brown or gray (E. subg. Hippochaete (Milde) Baker) |
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(2) |
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Aerial stems lasting one year or less; main stem often branched in regular whorls; stomata located on surfaces of aerial branches, in several rows; strobili blunt apically; sheath teeth leathery, persistent, blackish brown or reddish brown (E. subg. Equisetum) |
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(5) |
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2 (1) |
Aerial stems irregularly undulate; main stem ca. 0.6 mm in diam., solid and without longitudinal canals in center, 7- or more ridged, with 3(-5) sheath teeth. |
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10 E. scirpoides |
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Aerial stems not irregularly undulate; main stem more than 1 mm in diam., hollow and with longitudinal canals in center, 6-ridged, with 6 or more sheath teeth |
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(3) |
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3 (2) |
Mature main stem branched in whorls; sheath tubes grayish white or slightly reddish brown at apex. |
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7 E. ramosissimum |
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Mature main stem unbranched or rarely branched but not in whorls; sheath tubes blackish brown at apex |
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(4) |
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4 (3) |
Main stem robust, 5-9 mm in diam. at middle, up to 1 m tall or taller; apices of sheath teeth falling off early; sheath teeth 2-ridged abaxially. |
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8 E. hyemale |
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Main stem slender, (1-)2-3(-4) mm in diam. at middle, 18-50 cm tall; sheath teeth persistent, 4-ridged abaxially. |
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9 E. variegatum |
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5 (1) |
Aerial stems monomorphic, fertile stems same as sterile stems morphologically or young fertile stems slightly different from sterile branches |
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(6) |
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Aerial stems dimorphic, fertile stems without or with few shorter and finer whorled branches, obviously different from sterile branches |
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(8) |
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6 (5) |
Plants large; aerial branches 40-60 cm, main stem 3-6 mm in diam. at middle; internodes of lower 1-3 nodes of main stems reddish brown, lustrous; main stem not branched in whorls or branched in whorls but branches much thinner than main stem. |
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3 E. fluviatile |
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Plants small; aerial branches 10-30 cm, main stem 1-2 mm in diam. at middle; internodes of lower 1-3 nodes of main stems blackish brown, not lustrous; main stem branched in whorls |
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(7) |
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7 (6) |
Two sides of ridges of main stem and lateral branches with raised edges; upper main stem and lateral branches with 1 row of tubercles reaching apex of sheath teeth and a deep groove going through back of sheaths. |
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1 E. diffusum |
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Two sides of ridges of main stem and lateral branches rounded, with neither edges nor tubercles (but only laterally cut); groove shallow, going through back of sheaths. |
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2 E. palustre |
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8 (5) |
Main sterile branch plus lateral branches narrower than 10 cm; whorled lateral branches of sterile branch pointing upward and forming a 30?or smaller angle with main stem; lateral branches approximately half of main stem in diam.; main stem branched or unbranched below middle; fertile branch unbranched. |
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6 E. arvense |
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Main sterile branch plus lateral branches up to 20 cm wide; whorled lateral branches of sterile branch pointing laterally or slightly upward and forming a 45?90?angle with main stem; lateral branches much thinner than half of main stem in diam.; main stem unbranched below middle; fertile branch eventually branched |
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(9) |
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9 (8) |
Sheath teeth of sterile branch (2 or)3-5-lobed; lobes ovate-deltoid, reddish brown, two sides of ridges often with bristlelike protuberances; sheath teeth of lateral branches open. |
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4 E. sylvaticum |
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Sheath teeth of sterile branch 14-22-lobed; lobes narrowly deltoid, blackish brown at middle and light brown on margins, two sides of ridges often with tubercles; sheath teeth of lateral branches not open. |
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5 E. pratense |
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