1 Plants prostrate, with scape very short, holding bract (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 blade typically < 6 cm long; petal 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 blade typically > 7 cm long; petal (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 scape holding bract (leaves) well above ground, or sometimes bract tips barely touching the ground in early anthesis; floral fragrance various, foetid, pleasant, or mildly unpleasant

      4 Sepal abruptly deflexed between and below the leaves, distinctly descending below the approximately horizontal plane of the leaves; filament about as long as incurved anther; [T. recurvatum group].

        5 Anther connective slightly incurved or erect; filament 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; filament less than ½ as long as the ovary; stigma lobe 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; filament about equal to the ovary; stigma lobe 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 connective strongly incurved; filament 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 sepal); petal 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 sepal); petal usually ca. 2× as long as wide, attenuate to weakly clawed

      4 Sepal erect, ascending, or spreading, usually borne at or above the approximately horizontal plane of the leaves; filament much shorter than the upright anther.

               8 Petal 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 Petal erect to slightly spreading, not spirally twisted; anther dehiscence introrse (toward the inside of the flower), or latrorse (toward the side).

                 9 Petal broadly spatulate, clawed, broadly rounded (though sometimes with an apiculus) at the tip; petal pale lemon-yellow (the claw 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 Petal lanceolate, elliptic, obovate, or oblanceolate, but not broadly spatulate and distinctly clawed, generally acute at the tip; petal maroon-red, purplish-brown, yellow, or green; flower fragrance various; [collectively widespread in our area].

                   10 Stigma > 1.5× as long as the ovary; stamen about 0.5× as long as the petal; anther connective prominently prolonged into a beak 1.0-5.0 mm long (beyond the anther sac); [T. sessile group]

                   10 Stigma as long as the ovary or shorter; stamen < 0.5× as long as the petal; anther blunt, the connective extended < 1.0 mm beyond the anther sac.

                     11 Ovary ellipsoid; leaves acute, the margin 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; petal 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); petal 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 margin 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 Petal < 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); petal maroon, bronze, green, yellow; portions of ovary and stamen purplish during anthesis

                          13 Petal > 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 stomate across the surface (visible as white dots with 10× magnification); stamen ca. 1.5× as long as the ovary

                                16 Leaf apices acute; leaf upper surface lacking stomate (or present only near apex); stamen ca. 2× as long as the ovary

                              15 [of TX, LA, MS, AL, GA, SC, and FL]

                                  17 Ovary 3-angled at base of stigma (rarely 6-angled); petal 7-17 mm wide, narrowly spatulate (appearing clawed); outer whorl of stamen broader, anther dehiscence introrse; flower fragrance faintly spicy-fragrant, banana-like; [of AL, n. FL, GA, and e. SC]

                                  17 Ovary 6-angled; petal 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 Stamen ca. 2× as tall as the ovary; [of w. LA and e. TX]

                                    18 Stamen <1.5× as tall as the ovary; [of c. and e. LA and w. MS].

                                       19 Petal 3-5 mm wide; anther dehiscence introrse; anther connective extending 1-1.5 mm beyond the anther sac

                                       19 Petal 4-8 mm wide; anther dehiscence latrorse; anther connective scarcely extending beyond the anther sac