FNA Key to E. palustris complex

This is the portion of the key to Eleocharis species in Flora of North America that pertain to the E. palustris complex. 

Users of this treatment should be aware of the following: culms that are smooth when fresh are often ridged when dry; culms of pressed specimens are often flattened and must be carefully rehydrated and sectioned to determine the original cross-section shape; culm widths given here are usually for culms pressed flat; floral scale widths are measured on flattened scales or by doubling the width measured on scales folded along the midrib; and achene length does not include the tubercle, which is often included in descriptions published elsewhere.

12 (4) All or some culms with distal leaf sheath apex with distinct, abrupt tooth.   (13)
+ All culms with distal leaf apex without distinct, abrupt tooth.   (16)
       
13 (12) Culms hollow with complete transverse septa usually evident without sectioning culm; spikelets with 100500+ scales, 1540 per mm of rachilla; rhizomes mostly hidden by culms and roots, 3 mm thick.   Eleocharis montana
(not part of E. palustris complex,
not found in SK)
+ Culms spongy, the transverse septa incomplete; spikelets with 5200 scales, 310 per mm of rachilla; rhizomes evident, not hidden by culms and roots, 12 mm thick.

  (14)
14 (13) Proximal scale of spikelets clasping (2/3)3/4 (rarely all) of culm; subproximal scale of some (rarely all) spikelets without flower (empty); culms usually distinctly compressed; achenes smooth at 30X or finely rugulose at 1020X; tubercles as high as wide or higher.   Eleocharis macrostachya
(not reported in SK, 
but found in neighbouring provinces 
and states so expected to be found here)
+ Proximal scale of spikelets clasping all of culm (amplexicaulous); subproximal scale of all spikelets with flower; culms terete; achenes finely rugulose at 10X; tubercles sometimes lower than wide.   (15)
       
15 (14) Tubercles 0.150.3(0.5) mm, mostly much lower than wide; achenes finely rugulose at 10X; Atlantic and Gulf coastal plains.   Eleocharis ambigens 
(a coastal species, not found in SK)
+ Tubercles 0.350.65 mm, mostly at least as high as wide; achenes smooth at 30X or finely rugulose at 1030X; widespread.   Eleocharis erythropoda,
common in SK
       
16 (12) Proximal scale of spikelets clasping 2/3(3/4) of culm; all spikelets with empty subproximal scale.   (17)
+ Proximal scale of spikelets clasping 3/4+ of culm; subproximal scale with flower or empty.   (18)
       
17 (16) Perianth bristles (4)56(8), exceeding tubercle; achene apex without distinct neck, tubercles sessile on achenes; mostly boreal.   Eleocharis mamillata
(Harms says no SK specimens, 
FNA says found in SK, 
found in neighbouring provinces and states 
so
certainly
expected to be found here)
+ Perianth bristles 04(5), rarely exceeding tubercle; achene apex with or with out distinct neck, tubercles often not sessile on achenes; widespread.   Eleocharis palustris,
very common in SK
       
18 (16) Subproximal scale of some spikelets of plant empty; proximal scale of some or all spikelets usually clasping less than all of culm.   Eleocharis macrostachya
(not reported in SK, 
but found in neighbouring provinces and 
states so expected to be found here)
+ Subproximal scale of all spikelets of plant with flower; proximal scale of all spikelets clasping all of culm (amplexicaulous).   (19)
       
19 (18) Tubercles more than 2/3 as high and wide as achene, usually with vertical rows of prominent depressions when fully mature; floral scales 23 mm wide, 12 per mm of rachilla; boreal and subarctic coasts.   Eleocharis kamtschatica
(a coastal species, not found in SK)
+ Tubercles less than 2/3 as high and wide as achene, usually without vertical rows of depressions; floral scales 1.52(2.5) mm wide, (2)35 per mm of rachilla; ranges various.   (20)
       
20 (19) Tubercles mostly wider than high, 0.150.3(0.5) mm; achenes finely rugulose at 10X; Atlantic and Gulf coastal plains.   Eleocharis ambigens
(a coastal species, not found in SK)
+ Tubercles mostly at least as high as wide, 0.350.8 mm; achenes smooth at 30X or finely rugulose at 1030X; widespread.   (21)
       
21 (20) Floral scales in middle of spikelet not more than 1.8 mm wide, 4 5 per mm of rachilla.   Eleocharis erythropoda,
common in SK
+ Floral scales in middle of spikelet 1.82.5 mm wide, 24 per mm of rachilla.   Eleocharis uniglumis
(No verified specimens found in SK, 
but found in neighbouring provinces and 
states so expected to be found here)