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Show caption*© Alan Cressler: Isoetes piedmontana (likely identification), Hood Road Flatrock, Walton County, Georgia 1 by Alan Cressler | |
2 Leaves gray-green to bright-green; megaspore surface ridged or tuberculate, < 525 μm in diameter; [in acidic substrates]. | |
3 Plants 10-15 cm tall, individual plants apparent; leaf bases often with shiny black phyllopods; velum coverage < 30%; megaspores white to light gray, 400-525 μm in diameter. | |
4 Megaspores typically 440-510 μm in diameter; ornamentation pattern wrinkled to low tuberculate; [plants on granite outcrops]; [4n: Piedmont of e. AL (and w. GA?)] | |
4 Megaspores typically < 450 μm in diameter, ornamentation pattern sparsely wrinkled, short-ridged (some with pseudo-reticulate configuration) or densely tuberculate; [plants on granite or sandstone outcrops]; [2X: Piedmont of e. AL to s. VA; 4n populations reported in s. GA and se. VA] | |
3 Plants 2-10 cm tall; individuals densely clustered or mat-forming, often not readily discernable; leaf bases pale (black phyllopods absent); velum coverage > 70% (as little as 25% in Isoetes species 1); megaspores light gray to black, < 400 μm in diameter. | |
5 Plants 3-8 (-10) cm tall; velum coverage 40-60% (occasionally as little as 25%); megaspores olive-gray to brown; [2n: Lancaster County, Piedmont of SC] | |
5 Plants 2-4 (-7) cm tall; velum coverage 70-100%; megaspores pale gray to black. | |
6 Plants in large, sometimes densely clustered colonies, 3-5 (-7) cm tall, with globose rootstocks (some with elongated rootstalks); megaspores ± dull, densely ornamented with fine, often low and/ or obscure tubercles; [2n: Piedmont of GA] | |
6 Plants in dense, continuous mats; frequently joined, 2-3 (-4) cm tall, with elongated rootstalks (no globose rootstocks); megaspores ± shiny, unornamented or obscurely wrinkled; [2n: Piedmont of GA] | |
Show caption*© Alan Cressler: Isoetes lacustris, Piseco Lake, Little Sand Point State Campground, Adirondack Park, Hamilton County, New York 3 by Alan Cressler | |
7 Megaspores > 575 μm in diameter, with reticulate ornamentation. | |
8 Velum coverage < 30%; plants with leaves 15-20 cm long in fast-flowing open streams; [Mountains of TN or VA and northwards]. | |
9 Megaspore muri unevenly tall in congested, broken-reticulate pattern; [10n: n. VA, n. NJ northwards] | |
8 Velum coverage > 30%; plants with leaves 20-45 cm long in slow-flowing woodland stream channels; [Coastal Plain of GA, FL, and AL]. | |
7 Megaspores < 575 μm in diameter; with conspicuously echinate (spiny), reticulate, nearly spiny, low tuberculate and/or vermiform (worm-like) ornamentation. | |
11 Velum coverage > 40% (uncommonly to ± 30% in Isoetes valida). | |
12 Plants with broad (1.25-2.25 mm wide), light yellow-green, ± firm, reflexed leaves; velum coverage 45-70% (uncommonly only 30%); megaspores with tall, uneven, thin muri in ragged-reticulate pattern; [2n: found in woodland seepages (less commonly in pools); [primarily Mountains, uncommonly of Piedmont and Coastal Plain, PA to s. AL; also ne. MS] | |
12 Plants with narrow (1.0-1.5 mm wide), dark-green, straggly to widely reflexed leaves; velum coverage 80-100%; megaspores with low tubercles or broad ridges (mounds) of even height in broken to evenly reticulate pattern; [Coastal Plain]. | |
14 Megaspores < 450 μm in diameter, with coarse ornamentation pattern of broad tubercles or loosely interconnected vermiform mounds; leaves ca. 1.0 mm wide; [2n: FL, sw. GA, se. AL Coastal Plain] | |
11 Velum coverage < 40%. | |
16 Megaspore ornamentation of semi-reticulate pattern or with (usually obscure) tubercles; megaspores 440-480 (-520) μm in diameter (tetraploids). | |
17 Leaves firm, ± stiffly erect (Juncus-like); sporangium heavily brown-streaked and with 20-40% velum coverage; megaspore surface smooth, prominently ornamented with broad, often vermiform muri; [4n: s. GA Coastal Plain] | |
17 Leaves reflexed to loosely erect; sporangium ± unmarked and with ca. 10% velum coverage; megaspore surface mealy, sparsely to (uncommonly) densely ornamented with ± obscure tubercles and/or narrow muri; [4n: Piedmont, s. VA and n. NC] | |
16 Megaspore ornamentation plain or with irregular pattern of distinct, often numerous tubercles; megaspores < 440 μm in diameter (diploids). | |
18 Megaspores < 360 μm in diameter; megaspores ornamented with dense pattern of ± narrow, short muri; velum coverage 15-35%. | |
20 Narrow (± 1 mm wide) gray-green leaves with shiny, black-brown bases when spores are mature; megaspores ± 380 μm in diameter in diameter; typically with plain and mealy surface or obscurely ornamented with scattered tubercles and ridges; [2n: wet prairies and open graminoid swales of s. MS, w. AL and westward | |
15 Megaspore ornamentation in distinctly reticulate (‘honeycomb’) pattern or with thin sharp spines or otherwise dense pattern of tall, short-crested, almost echinate muri. | |
21 Plants emergent or aquatic; megaspores ± 460 (occasionally to 500) μm in diameter; evenly-reticulate ornamentation pattern of even-topped muri continuous to the equatorial ridge without an equatorial band; [2n: Atlantic Coastal Plain, Appalachian Mts and irregularly northward, south to c GA, ne AL] | |
21 Plants primarily emergent or amphibious; megaspores > 520 (rarely to over 600) μm in diameter; unevenly-reticulate and interrupted ornamentation pattern of ragged-topped muri, with an equatorial band of few to numerous spines; [4n or 6n]. | |
22 Megaspores primarily reticulate, often bearing tubercles or some equatorial spines but not densely echinate throughout; [collectively widespread] | |
23 Leaves narrow (< 2.0 mm wide), blackish-green to olive green; megaspore ornamentation broken-reticulate to almost spiny with numerous tubercles often with short, mostly stand-alone muri or with broken ridges, usually with an equatorial band of numerous spines. | |
24 Leaves of mature plants 10-20 cm long, 1.25-2.0 mm wide, olive-green; velum coverage 25-30%; densely congested (uncommonly uncongested and low-reticulate) megaspore ornamentation pattern; emergent on tidal beaches. | |
25 Megaspore ornamentation densely congested with tubercles and moderately tall, narrow, short muri with uneven crests; [4n: Coastal Plain, VA northward] | |
25 Megaspore ornamentation open with few tubercles and with low, broad muri with even crests; [4n: Coastal Plain, s. VA to DC]. | |
23 Leaves broad (> 2.0 mm wide), dark green to bright green; megaspore ornamentation moderately to evenly reticulate with few or no standalone short muri or tubercles, usually with equatorial band absent or a plain band with few spines. | |
27 Irregularly reticulate megaspore ornamentation pattern of both interconnected, longer muri and short, stand-alone muri; velum coverage ± 30% (occasionally less); plants usually deeply rooted (> 20% of leaf length) in clay or clayey-sand; [4n: Coastal Plain; LA, MS, AL] | |
27 Regularly reticulate megaspore ornamentation pattern of interconnected muri with few or no stand-alone muri; velum coverage 10-25%; plants usually shallowly rooted (10-20% of leaf length) in sand or silty-sand substrate. | |
28 Velum coverage 20-25%; megaspores with ± open, reticulate ornamentation pattern; [4n: Appalachian Mts and VA to AL Coastal Plain] | |
28 Velum coverage 6-10 (-20)%; megaspores with ± congested, densely reticulate ornamentation pattern; [6n: NC Coastal Plain] |