1a. Leaves simple (flowers in summer) --2. 1b. Leaves compound, or at least deeply cleft --4. 2a. Leaves linear, sword-shape (4-10 dm. tall; flowers greenish-white) =Rattlesnake Master, Eryngium yuccifolium.= 2b. Leaves kidney-shape or almost circular (stems creeping, about 1 dm. high; flowers white) (Water Pennywort) --3. 3a. Leaves peltate, attached by the center =Water Pennywort, Hydrocotyle umbellata.= 3b. Leaves not peltate, attached by the margin =Water Pennywort, Hydrocotyle americana.= 4a. Flowers yellow or purple --5. 4b. Flowers white or greenish --13. 5a. Leaf-segments entire (4-8 dm. high) --6. 5b. Leaf-segments toothed or incised --7. 6a. Leaf-segments filiform (summer) =Fennel, Foeniculum vulgare.= 6b. Leaf-segments ovate to lanceolate =Golden Alexander, Taenidia integerrima.= 7a. Leaves pinnately compound; some of the leaflets incised or pinnatifid --8. 7b. Leaves ternately compound; the segments crenate or serrate --9. 7c. Leaves deeply palmately cleft or divided; flowers in head-like umbels --18a. 8a. Leaf-segments obtuse, rounded, or cordate at the base (6-15 dm. high; summer) =Wild Parsnip, Pastinaca sativa.= 8b. Leaf-segments narrowed to the base (4-8 dm. high; spring) =Prairie Parsley, Polytaenia nuttallii.= 9a. Terminal leaflets conspicuously stalked, their total length, including stalk, at least 50% greater than the length of the lateral leaflets (Meadow Parsnip) --10. 9b. Terminal leaflets not conspicuously stalked, their total length, including stalk, about equaling the lateral leaflets (4-8 dm. high; late spring) (Golden Alexander) --12. 10a. Flowers purple (4-8 dm. high; early summer) =Meadow Parsnip, Thaspium aureum var. atropurpureum.= 10b. Flowers yellow --11. 11a. Stem-leaves once-ternate; leaflets finely serrate (4-8 dm. high; early summer) =Meadow Parsnip, Thaspium aureum.= 11b. Many stem-leaves 2-3-ternate; leaflets coarsely serrate or incised (6-12 dm. high; early summer) =Meadow Parsnip, Thaspium barbinode.= 12a. Basal and lower stem-leaves 2-3-ternate =Golden Alexander, Zizia aurea.= 12b. Basal leaves simple; stem-leaves once-ternate =Golden Alexander, Zizia cordata.= 13a. Leaves once-pinnate (or the submerged leaves decompound, if present) (summer) --14. 13b. Leaves ternately, palmately, or 2-3-pinnately compound --16. 14a. Leaflets mostly ovate or ovate-lanceolate, some of them coarsely incised (3-9 dm. high) =Water Parsnip, Berula erecta.=