5(4). Fruits oblong to ellipsoid, less than twice as broad as long (6) 



5. Fruits linear to oblong, more than twice as long as broad (19) 



6(5). Pericarp not corky-thickened; fruit ribs filiform to prominent, never corky 

 (7) 



6. Pericarp of some or all of the fruit ribs corky-thickened (14) 



7(6). Perennials; leaflets not pinnately dissected; stylopodium lacking (8) 



7. Annuals or biennials; leaflets usually pinnately dissected; stylopodium de- 



pressed-conic to conic (9) 



8(7). Plants acaulescent; calyx teeth minute; seed face deeply sulcate 



4. Tauschia 



8. Plants caulescent, branching; calyx teeth prominent; seed face slightly con- 



cave 12. Zizia 



9(7). Involucre present; fruit ribs undulate, crenate; oil tubes very small, numer- 

 ous, irregular; stems variously spotted 14. Conium 



9. Involucre lacking (sometimes a few bracts in Perideridia) (10) 



10(9). Involucel lacking (11) 



10. Involucel present; low diffuse annuals (13) 



11(10). Flowers yellow; plants with aniselike odor 11. Foeniculum 



1 1 . Flowers white or pinkish; plants without aniselike odor (12) 



12(11). Plants from slender elongate roots; umbels axillary or terminal; calyx 

 lobes inconspicuous 13. Apium 



12. Plants from fascicled tuberous or fusiform roots; umbels terminal; calyx 



lobes conspicuous 1 5. Perideridia 



13(10). Fruit ribs filiform, rounded, subequally spaced; plants glabrous 



3. Spermolepis 



13. Fruit ribs acute, the lateral of the two mericarps contiguous and appearing 



to form a single rib; plants roughened 5. Ammoselinum 



14(6). Perennials; pericarp or at least some of the dorsal as well as the lateral 

 fruit ribs corky-thickened (15) 



14. Annuals; only the lateral fruit ribs corky-thickened (17) 



15(14). Fruit ribs obscure in the corky-thickened pericarp; plants stoloniferous 

 16. Berula 



15. Fruit ribs prominent, corky-thickened; plants not stoloniferous (16) 



16(15). Involucre prominent; rays few; fruit ribs subequal in cross section 



17. Sium 



16. Involucre inconspicuous or lacking; rays usually numerous; fruit ribs un- 



equal in cross section 18. Cicuta 



17(14). Leaves decompound with filiform divisions 20. Ptilimnium 



17. Leaves entire, palmately parted or pinnate, with narrow elongate divisions 



(18) 



18(17). Fruit prominently beaked; cauline leaves palmately parted; petals with 

 a narrower inflexed apex 21. Cynosciadium 



18. Fruit rounded at apex; leaves entire or pinnate; petal apex not inflexed 



22. Limnosciadium 



19(5). Fruits without secondary ribs ( 20 ) 



19. Fruits with prominent corky or bristly secondary ribs, the primary ribs ob- 



scure 9. Trepocarpus 



1213 



