Flora of the Southeastern United States
2022 Edition

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Key to Thaspium

1 Leaves 3-4-ternate, the very numerous ultimate segments 1-3 mm wide; petals white (fading to yellowish tan in older herbarium material).
..2 {morphological characters to be added}; [w. NC, e. TN, and nw. GA]
..2 {morphological characters to be added}; [KY]
1 Leaves simple, 3-foliolate, or 2-3-ternate, the final leaflets or segments > 5 mm wide; petals yellow, maroon, or pale yellow.
....3 Basal leaves at least in part 2-ternate or more divided (with 5 or more leaflets).
......4 Leaflets coarsely and rather lacerately serrate or incised, many of the teeth at least 2 mm long as measured on the shorter side; leaflet margins ciliate, not hyaline-whitened; umbel rays 8-10, < 3.5 cm long even in fruit; petals pale to creamy yellow; plant hispidulous to sparsely pubescent.
........5 Stem leaves 1-2-ternate, glabrous or glabrate on the lower surface except for the primary veins; corolla golden yellow; peduncles and umbel rays glabrous or papillose-roughened on upper surface; fruits glabrous between and on the wings, mature fruit 5-6 mm long
........5 Stem leaves 2-3-ternate, puberulent on the lower surface on the veins and blade surface; corolla pale yellow to creamy white; peduncles and umbel rays scabrellous on upper surface; fruits scabrellous between and sometimes on several wings, mature fruit 4-5 mm long
......4 Leaflets finely to coarsely serrate, but not lacerate or incised, few if any of the teeth > 2 mm long as measured on the shorter side; leaflet margins glabrous and hyaline-whitened; umbel rays mostly either more in number (than 8-10) or longer (than 3.5 cm long); petals golden yellow; plant glabrous.
..........6 Teeth of the leaflets fine, averaging (4-) 5-10 per cm of margin, acuminate (the 2 sides making an angle of about 45 degrees); umbel rays (8-) 10-18, in fruit 2.5-4 (-5) cm long; basal leaves many-foliolate, the leaflets mostly acuminate; fruit ca. 2× as long as wide
..........6 Teeth of the leaflets coarse, averaging (1-) 2-3 (-4) per cm of margin, acute to obtuse (the 2 sides making an angle of about 90 degrees); umbel rays 4-10 (-12), the longest to 11 cm long in fruit (some on a plant at least 5 cm long); basal leaves 3-5 (-7)-foliolate, the leaflets mostly rounded to obtuse at the apex; fruit 1-1.5× as long as wide
....3 Basal leaves simple or 3-foliolate (with 1-3 leaflets).
............ 7 Teeth of the leaflets coarse, averaging 2-3 (-4) per cm of margin, the long side of most of the teeth 2-10 mm long; basal leaves mostly 3-foliolate (or more divided); middle and upper stem leaves equally or more divided than the basal leaves (the most divided leaves usually those of the mid-stem)
............ 7 Teeth of the leaflets fine, averaging 4-10 per cm of margin, the long side of most of the teeth 0.5-2 (-4) mm long; basal leaves simple (and cordate) or 3-foliolate; middle and upper stem leaves 3-foliolate (rarely simple).
............ ..8 Teeth relatively acute, without a well-developed callous tip and a thickened, translucent border (use 10× magnification); lower portion of stem puberulent, the upper nodes also usually puberulent (use 10×); leaf margins often ciliolate; umbel rays 7-15; flowers golden yellow
............ ..8 Teeth relatively obtuse, with a well-developed callous tip and a thickened, translucent border (use 10× magnification); lower portion of stem glabrous, the upper nodes sometimes minutely roughened; leaf margins glabrous and hyaline; umbel rays 4-10 (-11); flowers maroon or golden yellow.
............ ....9 Flowers golden yellow; stems and leaves green, rarely purple-tinged
............ ....9 Flowers dark maroon; stems and leaves usually purple-tinged