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| 1 Leaves linear, lanceolate, or oblancolate, > 4× as long as wide. |
| ..2 Leaves phyllodial (septate, hollow or flat, segmented); flowers white or purple; [plants of wetlands]. |
| ....3 Umbels simple; leaves spatulate, broader towards the tip, often somewhat flattened in ×-section, rounded or obtuse at the apex |
| ....3 Umbels compound; leaves tapering to a pointed tip, either flat or terete in ×-section. |
| ......4 Leaves flat in ×-section, with obvious parallel venation and less obvious septae / cross-partitions |
| ......4 Leaves terete in ×-section, the septae obvious. |
| ........5 Plants 1-11 dm tall, annuals, sometimes mat-forming and adventiously perennial; fruits 1-3 mm long, with lateral ribs; rays 3-15 |
| ........5 Plants 6-24 dm tall, perennials from rhizomes or tubers; fruits 4-9 mm long, with lateral wings; rays 5-20 |
| ..2 Leaves “normal” (non-septate, flat, continuous, and in some cases lobed, toothed, or spinose-margined); flowers blue, yellow, white, or whitish-green; [plants of wetlands or uplands]. |
| ..........6 Flowers borne in involucrate heads; corolla blue or greenish-white |
| ..........6 Flowers in compound umbels; corolla yellow or white. |
| ............ 7 Stem leaves similar to the basal, all simple; corollas yellow; [alien, of disturbed areas] |
| ............ 7 Stem leaves palmately 3-5-foliolate with linear leaflets, differing from the simple basal leaves; corollas white; [native, of blackland prairies and associated disturbed areas, from AL and TN westward] |
| 1 Leaves orbicular, ovate, or elliptic, < 4× as long as wide. |
| ............ ..8 Leaves orbicular, about as wide as, or wider than, long; base peltate or cordate. |
............ ....9 Leaves leathery, with spinose margins; inflorescence a head; flowers blue; [rare introduction] |
| ............ ....9 Leaves herbaceous or somewhat fleshy. toothed or lobed, but not spinose; inflorescence umbellate or verticillate; flowers white, greenish, or purplish; [collectively common and widespread]. |
| ............ ......10 Foliage and fruits (or ovaries) stellate-pubescent or glochidiate; leaves lobed, but otherwise entire; [rare alien] |
| ............ ......10 Foliage and fruits (or ovaries) glabrous; leaves toothed, sometimes also lobed; [common natives and aliens] |
| ............ ..8 Leaves ovate or elliptic, 1.2-4× as wide as long; base cordate, peltate, or truncate. |
| ............ ........11 Leaves perfoliate; flowers yellow; [rare aliens]. |
| ............ ..........12 Stem leaves entire; umbellets subtended by broad foliaceous bractlets |
| ............ ..........12 Stem leaves serrate; umbellets lacking bractlets |
| ............ ........11 Leaves cordate or truncate at the base; flowers white, green, yellow, blue, or purple; |
| ............ ............ 13 Flowers greenish or blue; leaves all simple (sometimes stem leaves lobed); inflorescence a head or very congested (subcapitate) umbel; [plants of wetland situations, prostrate, creeping, or erect]. |
| ............ ............ ..14 Inflorescence a very congested (subcapitate) umbel, with 4-9 flowers; leaves cordate at the base, long-petiolate, the petioles characteristically 2× as long as the leaf |
| ............ ............ ..14 Inflorescence a head, with > 20 flowers; leaves cuneate to truncate at the base, sessile to short petiolate, the petioles < 1× as long as the leaf (except E. prostratum) |
| ............ ............ 13 Flowers yellow or purple; basal leaves simple, stem leaves usually compound; Inflorescence a compound umbel; [erect plants of upland situations]. |
| ............ ............ ....15 Fruits (partly to fully mature) with thin-edged wings; flowers yellow or purple; central flower of each umbellet staminate and pedicelled; fruits all pedicelled in all umbellets |
| ............ ............ ....15 Fruits ribbed (with rounded, cordlike ribs), lacking thin-edged wings; flowers yellow; central flower of each umbellet either staminate and pedicelled, or pistillate and sessile; fruits all pedicelled in some umbellets (those with a staminate central flower), or the central fruit sessile in some umbellets (those with a pistillate central flower) |
| 1 Inflorescence unbranched, the heads solitary on peduncles from the leaf axils of the prostrate to erect stem. |
| ..2 Leaves pinnately lobed or dissected |
| ..2 Leaves entire, irregularly toothed (rarely with some minor, irregular lobing). |
| ....3 Heads subglobose or hemispherical when fully developed, about as wide as long; bracts subtending the head barely extending beyond the base of the head; main stems leaves linear, narrowly elliptic, narrowly oblanceolate, sometime tricuspid apically |
| ....3 Heads cylindrical, longer than wide; bracts subtending the head longer than the radius of the head, thus extending conspicuously beyond the base of the head; main stem leaves elliptic, broader than above |
| 1 Inflorescence branched, the heads in a cyme borne terminally on the erect or prostrate stem. |
| ......4 Basal and cauline leaves unlobed (except sometimes the uppermost; note that bracts in the inflorescence are often lobed), 3-100 cm long; leaf margins without coarse spine-tips (finely spinulose in E. foetidum). |
| ........5 Basal leaves evenly and rather finely toothed with spine-tipped teeth |
| ........5 Basal leaves with entire or crenate margins, lacking spiny tips (though in some species with flexible bristles along the margins). |
| ..........6 Blades of basal and lower cauline leaves 3-7 (-10) cm long, acute to obtuse apically, cordate to truncate basally, with a length/width ratio of 1.5-3 (-6) |
| ............ 7 Head hemispheric, about as wide as high; [native, seeps, bogs, and wet pine savannas, VA, KY, AR, and OK southwards] |
| ............ 7 Head ovoid, taller then wide; [non-native from horticultural use] |
| ..........6 Blades of basal and lower cauline leaves 10-100 cm long, acuminate to acute apically, clasping basally, with a length/width ratio of 5-50. |
| ............ ..8 Leaves with primary veins pinnate-reticulate, with or without marginal bristles; flowers blue. |
| ............ ....9 Styles 3.0-4.0 mm long at maturity, scarcely exceeding the bractlets (which subtend each flower); heads subglobose to hemispherical, 6-12 mm in diameter; middle cusp of the bractlets elongate, distinctly longer than the lateral cusps |
| ............ ....9 Styles 4.0-6.0 mm long at maturity, exceeding the bractlets; heads globose, 9-15 mm in diameter; middle cusp of the bractlets about equal in length to the lateral cusps |
| ............ ..8 Leaves with primary veins parallel, with marginal bristles; flowers greenish-white. |
| ............ ......10 Larger leaves < 1.5 cm wide; marginal bristles in fascicles of 1-3 (-4), those on the lower portion of the leaf usually in fascicles of 2-3 |
| ............ ......10 Larger leaves > 1.5 cm wide; marginal bristles of leaves solitary |
| ............ ........11 Plant green; marginal bristles triangular (broadened at the base); flowering late |
| ............ ........11 Plant glaucous; marginal bristles acicular; flowering early |
| ......4 Basal and cauline leaves (all, or at least many of the cauline) definitely deeply lobed into 3 or more divisions, < 10 cm long; leaf lobes tipped with moderately stiff to very stiff spine tips. |
............ ..........12 Leaves thickly coriaceous, glaucous blue, palmately lobed, about as wide as long |
| ............ ..........12 Leaves herbaceous to stiff, green to slightly glaucous, pinnately toothed or lobed. |
| ............ ............ 13 Heads blue; basal leaves serrate but not divided. |
| ............ ............ ..14 Heads 20-35 mm tall, purple to reddish; heads capped with conspicuous (1-2 cm long) spinescent bracts |
| ............ ............ ..14 Heads 4-15 mm tall, bluish to purplish; heads capped with a few, mostly entire, spinescent bracts, or lacking them. |
| ............ ............ ....15 Plants erect, stem solitary, branching upwards; fruits 1-2 mm long |
| ............ ............ ....15 Plants diffuse, decumbent, branched from the base and upwards; fruits 1.5-3 mm long |
| ............ ............ ......16 Cauline tips absent; mericarps 1.5-2 mm long |
| ............ ............ ......16 Cauline leaves present, spine tipped; mericarps 2.5-3 mm long |
| ............ ............ 13 Heads greenish, whitish, or pale lavender; basal leaves pinnately or pinnately-ternately divided. |
| ............ ............ ........17 Plants stout, fleshy, usually glaucescent; basal leaves 10-25 cm long and wide, pinnately or pinnate-ternately divided into > 7 segments, the cauline leaves similar but reduced in size and number of divisions; heads 10-15 mm in diameter; [rare ballast waif of disturbed ground]; [subgenus Eryngium] |
| ............ ............ ........17 Plants slender, not fleshy, green; basal and cauline leaves 2-6 cm long, 3-5 (-7) pinnately parted; heads 5-8 mm in diameter; [native species of dry pinelands or scrub of the Coastal Plain of e. GA, s. AL, and FL]. |
| ............ ............ ..........18 Basal leaves pinnately lobed; stems decumbent at base, ascending (the mature plant often wider than it is tall); stems leafy throughout their length, usually with 10 or more leaves; [dry pinelands and scrub of the Coastal Plain of e. GA, s. AL, and FL] |
| ............ ............ ..........18 Basal leaves trilobed; stems ascending at base (the mature plant taller than wide); stems erect, unbranched; stems sparsely leafy, especially upwards, usually with 7 or fewer leaves; [endemic in Florida scrub in Highlands County, c. peninsular FL] |