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Key A: trilliums with sessile flowers and mottled leaves (subgenus Sessilia)

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1 Plants prostrate, with scapes very short, holding bracts (leaves) near the ground; floral fragrance of rotting meat or manure-scented
..2 Anther dehiscence extrorse; bract apices rounded or obtuse, typically mottled only in 2 colors, silver and green
..2 Anther dehiscence introrse; bract apices obtuse or acute, conspicuously mottled in silver and three or more shades of green
....3 Rhizome 0.3-1 cm in diameter, branching, forming clonal patches; scape straight, ascending, densely puberulent on angles; bract blades typically < 6 cm long; petals 1.5–3 cm in length, widest at middle; floral fragrance of horse manure
....3 Rhizome 0.8-1.5 cm in diameter, unbranched, not forming clonal patches; scape S-shaped, decumbent or semi-decumbent, glabrous; bract blades typically > 7 cm long; petals (2.2–) 3.0–5.0 (–6.0) cm in length, widest above the middle; floral fragrance of rotten meat
1 Plants erect or ascending, with tall scapes holding bracts (leaves) well above ground, or sometimes bract tips barely touching the ground in early anthesis; floral fragrance various, foetid, pleasant, or mildly unpleasant
......4 Sepals abruptly deflexed between and below the leaves, distinctly descending below the approximately horizontal plane of the leaves; filaments about as long as incurved anthers; [T. recurvatum group].
........5 Anther connectives slightly incurved or erect; filaments short (< ½ the anther length); [variously endemic to either Kershaw and Richland counties in the inner Coastal Plain of SC (Trillium oostingii) or Hamblen and Hawkins counties in the Ridge and Valley of TN (Trillium tennesseense)].
..........6 Ovary 6-16 mm long; filaments less than ½ as long as the ovary; stigma lobes ca. 1× as long as the ovary, the stigmatic surfaces smooth; [endemic to Kershaw and Richland counties in the inner Coastal Plain of SC]
..........6 Ovary 2-4 mm long; filaments about equal to the ovary; stigma lobes ca. 2× as long as the ovary, the stigmatic surfaces strongly crested-undulate; [endemic to Hamblen and Hawkins counties in the Ridge and Valley of TN]
........5 Anther connectives strongly incurved; filaments long, > ½ the anther length; [primarily west of the Blue Ridge and south into the Gulf Coastal Plain, very rarely disjunct to the Mountains or upper Piedmont].
............ 7 Leaves sessile or subsessile, borne in a descending or drooping manner (similar to the sepals); petals usually 4-7× as long as wide, strongly clawed
............ 7 Leaves distinctly petiolate, borne in an ascending manner (strongly contrasting in position with the strongly deflexed sepals); petals usually ca. 2× as long as wide, attenuate to weakly clawed
......4 Sepals erect, ascending, or spreading, usually borne at or above the approximately horizontal plane of the leaves; filaments much shorter than the upright anthers.
............ ..8 Petals spreading to horizontal, with 1-2 spiral twists (looking something like an airplane propeller); anther dehiscence extrorse (toward the outside of the flower); [T. sessile group]
............ ..8 Petals erect to slightly spreading, not spirally twisted; anther dehiscence introrse (toward the inside of the flower), or latrorse (toward the side).
............ ....9 Petals broadly spatulate, clawed, broadly rounded (though sometimes with an apiculus) at the tip; petals pale lemon-yellow (the claws greenish or maroon); flower fragrance clove-like; [of the Savannah River drainage, from sw. NC southeastward along the GA-SC border]; [T. sessile group]
............ ....9 Petals lanceolate, elliptic, obovate, or oblanceolate, but not broadly spatulate and distinctly clawed, generally acute at the tip; petals maroon-red, purplish-brown, yellow, or green; flower fragrance various; [collectively widespread in our area].
............ ......10 Stigmas > 1.5× as long as the ovary; stamens about 0.5× as long as the petals; anther connectives prominently prolonged into a beak 1.0-5.0 mm long (beyond the anther sacs); [T. sessile group]
............ ......10 Stigmas as long as the ovary or shorter; stamens < 0.5× as long as the petals; anthers blunt, the connectives extended < 1.0 mm beyond the anther sacs.
............ ........11 Ovary ellipsoid; leaves acute, the margins of the outer 1/3 more or less straight; leaf blade mottled with 3 or more shades of green, the palest shade forming a very conspicuous pale silvery-green streak along the midvein; [of the Coastal Plain and fall-line area of GA, AL, and FL Panhandle]; [T. sessile group].
............ ..........12 Stem 2.5-3× as long as the leaves; petals oblanceolate-obovate, usually 1.5-3× as long as wide; flower fragrance yeasty-sweet (or similar to overripe bananas)
............ ..........12 Stem 1-2× as long as the leaves (though sometimes elongating late in the season); petals narrowly elliptic to oblanceolate-obovate, usually 3-5× as long as wide; flower fragrance yeasty-sweet (or reminiscent of stale beer)
............ ........11 Ovary ovoid; leaves acute to acuminate, the margins of the outer 1/3 convex; leaf blade mottled with 2-3 shades of green, paler shades sometimes prominent along the midvein, but not as above; [collectively widespread in our area]; [T. maculatum group].
............ ............ 13 Petals < 4× as long as wide, elliptic-oblanceolate to oblanceolate; [of inland provinces, rarely in the Coastal Plain].
............ ............ ..14 Flower fragrance fruity-spicy, like green apples or Calycanthus (rarely musky); petals maroon, bronze, green, yellow; portions of ovary and stamens purplish during anthesis
............ ............ ..14 Flower fragrance lemon-like; petals greenish-yellow darkening to yellow; ovary and stamens greenish-white during anthesis
............ ............ 13 Petals > 4.5× as long as wide, narrowly oblanceolate-spatulate to linear-oblanceolate; [of the Coastal Plain, rarely farther inland].
............ ............ ....15 [of TX, OK, AR, MO, KS, and IL]
............ ............ ......16 Leaf apices blunt to rounded; leaf upper surface with numerous stomates across the surface (visible as white dots with 10× magnification); stamens ca. 1.5× as long as the ovary
............ ............ ......16 Leaf apices acute; leaf upper surface lacking stomates (or present only near apex); stamens ca. 2× as long as the ovary
............ ............ ....15 [of TX, LA, MS, AL, GA, SC, and FL]
............ ............ ........17 Ovary 3-angled at base of stigmas (rarely 6-angled); petals 7-17 mm wide, narrowly spatulate (appearing clawed); outer whorl of stamens broader, anther dehiscence introrse; flower fragrance faintly spicy-fragrant, banana-like; [of AL, n. FL, GA, and e. SC]
............ ............ ........17 Ovary 6-angled; petals 3-8 mm wide, linear-oblanceolate, narrowly elliptic, to linear-lanceolate (weakly or not clawed); flower fragrance putrid, like rotting meat; [of MS, LA, and e. TX].
............ ............ ..........18 Stamens ca. 2× as tall as the ovary; [of w. LA and e. TX]
............ ............ ..........18 Stamens <1.5× as tall as the ovary; [of c. and e. LA and w. MS].
............ ............ ............ 19 Petals 3-5 mm wide; anther dehiscence introrse; anther connective extending 1-1.5 mm beyond the anther sacs
............ ............ ............ 19 Petals 4-8 mm wide; anther dehiscence latrorse; anther connective scarcely extending beyond the anther sacs
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