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1 Petals dull, white; achenes roughly transverse-ridged; plants aquatic, the leaves finely dissected to merely shallowly lobed; [native, occurring in circumneutral waters]; [subgenus Auricomus; section Batrachium] |
1 Petals shiny, yellow (sometimes fading or bleaching to whitish); achenes usually not transverse-ridged (though often variously ornamented); plants aquatic or terrestrial, the leaves various; [native or introduced, occurring in various habitats]. |
..2 Cauline leaves all simple, mostly lanceolate, either entire, denticulate, or serrate, but not lobed or deeply divided; [native, occurring in marshes or other wetlands]; [subgenus Auricomus; section Flammula] |
..2 Cauline leaves (at least most them) lobed, divided, or compound; [native or introduced, occurring in various habitats]. |
....3 Basal leaves not divided, mostly cordate, reniform, or ovate (and merely toothed), distinctly unlike the deeply divided cauline leaves; achenes turgid, ovoid, 1-2.5 mm long, without pronounced marginal rims; petals 1.5-6.5 mm long; [native, occurring in mesic to dry forests and woodlands, and also (especially R. abortivus) weedy]; [subgenus Auricomus; section Auricomus] |
....3 Basal leaves mostly deeply parted or compound, the cauline leaves generally similar but smaller and often less divided; achenes various, 1-5 mm long, with or without pronounced marginal rims; petals 2-15 mm long; [native or introduced, occurring in various habitats]. |
......4 Achenes markedly spiny, papillose, or tuberculate (the protuberances few and small in R. sardous, keyed both here and below); [introduced, usually weedy and in disturbed habitats] |
......4 Achenes smooth (rarely pubescent or papillose); [native or introduced, occurring in various habitats]. |
........5 Achenes turgid, 1-1.5 (-2) mm long, the marginal rims scarcely or not at all evident, the achenes corky-thickened at their bases for dispersal by floating; [of mucky marshes or ditches, or aquatic in pools]; [subgenus Auricomus; section Hecatonia] |
........5 Achenes moderately turgid or flattened, 1.5-3.8 mm long, with a pronounced (at 10× or more) marginal rim appearing as a differentiated border or flange, more-or-less flattened, and separated from the central bulge of the achene by a concavity or even a groove, the achenes not corky-thickened at their bases; [of mostly terrestrial habitats or in bottomland forests] |
1 Petals 1-3 (-5); petals 1-2 mm long, about as long as the sepals; annual |
1 Petals (4-) 5-9; petals 2-8 mm long, distinctly longer than the sepals; annual or perennial. |
..2 Lower stem leaves 6-14 cm long; sepals 4-7 mm long; achene beaks 1.0-1.3 mm long |
..2 Lower stem leaves 1-6.5 cm long; sepals 1.5-4 mm long; achene beaks 0.1-0.6 mm long. |
....3 Achenes 0.8-1.0 mm long, lower stem leaves ovate to lanceolate, 4-24 mm wide. |
....3 Achenes 1.2-1.6 mm long; lower stem leaves linear to lanceolate, 0.4-8 mm wide. |
......4 Leaf blades 2-8 mm wide; stems 0.5-2 mm in diameter; sepals 2-3 mm long |
......4 Leaf blades 0.4-1.5 mm wide; stems 0.2-1.0 mm in diameter; sepals 1-2 mm long |
1 Achene beaks (0.6-) 0.7-1.0 mm long; petals < ½ as long as the sepals; sepals hirsute |
1 Achene beaks 0.1-0.3 mm long; petals > ½ as long as the sepals; sepals glabrous to sparsely long-villous. |
..2 Petals 4-8 mm long, longer than the sepals |
..2 Petals 1.5-3.5 mm long, slightly shorter than the sepals. |
....3 Leaves and stems glabrous or nearly so (or the upper stem puberulent); basal leaves 1-6 (-10) cm wide, reniform to cordate at the base; roots usually all filiform; receptacle surface (with achenes removed or fallen off) pubescent (at least sparsely so); achenes shiny |
....3 Leaves and stems villous, at least sparsely so and at least toward the base of the plant; basal leaves 1-2.5 cm wide, truncate to cuneate (rarely cordate) at the base; roots sometimes in part fusiform-thickened; receptacle surface glabrous; achenes dull |
1 Flowers sessile, opposite the petioles; sepals 3; petals 3; [section Polyanthemos] |
1 Flowers pedunculate, axillary; sepals usually 5; petals usually 5. |
..2 Petals 1-2 (-3) mm long; receptacles glabrous; [section Ranunculus] |
..2 Petals (3-) 4-12 mm long; receptacles pubescent. |
....3 Achenes bodies 1.5-3 mm long, 30-60 per head; achene beak ca. 0.5 mm long; achene with conical protuberances or short spines, to 0.16 mm long; achene beak 0.1-0.5 mm long; basal leaves compound; [section Polyanthemos]. |
......4 Achene with a few conical protuberances; petals 5-12 mm long; plant sparsely to densely hirsute; achenes 30-40 per head |
......4 Achene with numerous short spines; petals (3-) 4-5 mm long; plant with a few, widely scattered, long hairs; achenes 40-60 per head |
....3 Achenes 2.5-5 mm long, 4-20 per head; achene beak 1.5-3.0 mm long (or 0.8-1 mm long in R. marginatus); achene conspicuously spiny, the longer spines mostly 0.30-0.85 mm long (or only ca. 0.2 mm long in R. marginatus); basal leaves simple (but deeply lobed) or compound. |
........5 Achenes 4-9 per head, in a single whorl; achene margins spiny, as also the faces; beak of the achene 2.5-3 mm long; [section Echinella] |
........5 Achenes 10-20 per head, in several whorls; achene margins smooth, the spines restricted to the faces; beak of the achene 1.5-2.5 mm long; [section Polyanthemos]. |
..........6 Achene faces with short protuberances ca. 0.2 mm long; achene beak 0.8-1.0 mm long; peduncle usually longer than the subtending leaf |
..........6 Achene faces with stout spines ca. 0.5 mm long; achene beak 2.0-2.5 mm long; peduncle usually shorter than the subtending leaf |
1 Petals 2-6 mm long, about as long as the sepals; [section Polyanthemos]. |
..2 Basal leaves simple; achene beak strongly hooked |
..2 Basal leaves 3-foliolate; achene beak straight or nearly so. |
....3 Petals 4-6 mm long, 3.5-5 mm wide; achene beak 1.0-1.2 mm long; [WV northward] |
....3 Petals 2-4 mm long, 1.2.5 mm wide; achene beak 0.6-0.8 mm long; [widespread] |
1 Petals 5-15 mm long, (1.3-) 1.5× or more as long as the sepals; achene beak straight, flexuous, slightly curved, or hooked, 0.2-3.0 mm long. |
......4 Achene beaks recurved or hooked, the stigmatic surface elongate, along the upper (curved) side of the style (beak) (visible at 10×); [introduced, usually weedy in disturbed habitats]. |
........5 Stems repent, rooting at the nodes; [section Polyanthemos] |
........5 Stems erect, not rooting at the nodes. |
..........6 Petals 5-8 mm long; plant a soft-based annual; achene face usually with at least a few conical protuberances (if examined carefully at 10× or more); [section Polyanthemos] |
..........6 Petals 8-16 mm long; plant a cormose or hard-based perennial; achene face truly smooth. |
............ 7 Sepals spreading; stems not cormose-thickened at the base; larger leaves appearing (3-) 5-parted, all of the segments sessile; plant to 12 dm tall; [section Ranunculus] |
............ 7 Sepals tightly reflexed; stems cormose-thickened at the base; larger leaves pinnately 3-5-parted, the terminal segment long-stalked; plant to 6 dm tall; [section Polyanthemos] |
......4 Achene beaks straight or slightly curved, flexuous, the stigmatic surface limited to the tip of the style (beak); [native, normally in more-or-less natural habitats]; [section Polyanthemos]. |
............ ..8 Larger leaves mostly pinnately 3-7-foliolate, the terminal leaflet larger than the lateral leaflets, the leaflets (especially the terminal) often further cleft or lobed, the blade usually longer than wide in outline, the segments often rather narrow; naked receptacle conical, tapering gradually to the apex (the region of staminal attachment as thick as the region of gynoecial attachment, which tapers through all or nearly all of its length, best seen by stripping off the achenes); rhizome regenerating totally each growing season, producing both fibrous and (at the end of the growing season) tuberous roots (1.3-4.9 mm in diameter); [rare in our area, in calcareous, mafic, or ultramafic sites with prairie affinities] |
............ ..8 Larger leaves mostly palmately 3-foliolate, the terminal leaflet about the same size as the lateral leaflets, the leaflets sometimes further cleft or lobed, the blade usually as wide as long or wider; naked receptacle clavate or ellipsoid (the region of staminal attachment distinctly narrower than the region of gynoecial attachment, thus forming a waist, from which the gynoecial region expands and then tapers to the apex); rhizome regenerated partially each growing season, producing uniform, fibrous roots (up to 3.0 mm in diameter); leaves usually simple and ovate, or trifoliate with ovate leaflets; [collectively widespread in our area]. |
............ ....9 Achenes wide-margined (wider portions of the margin 1/4 to 2/3 as wide as the achene body); plants colonial, sending out stolons (by the time of fruiting) which root at the nodes, forming new plants; sepals reflexed at full anthesis |
............ ....9 Achenes narrow-margined (wider portions of the margin 1/8 or less as wide as the achene body); plants usually erect or repent by the time of fruiting (if repent sometimes forming adventitious roots at the nodes, but not generally developing new plants); sepals spreading at full anthesis (sometimes reflexed later). |
............ ......10 Plants repent; aerial shoots 50-80 (-91) cm long at time of fruiting; [generally of swamps and marshes] |
............ ......10 Plants erect; aerial shoots 14-45 (-60) cm long at time of fruiting; [generally of upland habitats] |