| 1. Peduncle generally < leaf; bractlets very large, >> umbels, wide, sharply pinnately lobed, leaf-like |
| T. howellii |
| 1' Peduncle > leaf; bractlets small, < to slightly > umbels, narrow, entire or nearly so, not leaf-like |
| |
| 2. Fruit oblong to narrowly elliptic, much longer than wide, ribs prominent, acute, ± wing-like; leaf ± leathery |
| |
| 3. Leaf 1-pinnate; rays unequal, spreading-ascending |
| T. arguta |
| 3' Leaf 2-pinnate; rays subequal, spreading and reflexed |
| T. parishii |
| 2' Fruit nearly round, ± as wide as long, ribs low, obtuse, thread-like; leaf not leathery |
| |
| 4. Plant glabrous, smooth; rays 512; pedicel 13 mm |
| T. glauca |
| 4' Plant minutely roughened; rays 1030; pedicel 215 mm |
| |
| 5. Several bractlets generally < flowers, fruits; fruit 47 mm, 45 mm wide |
| T. hartwegii |
| 5' All bractlets generally < flowers, fruits; fruit 35 mm, 46 mm wide |
| T. kelloggii
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