FLOWERING PLANTS AND FERNS OF ARIZONA 641 



18. Ribs not winged; leaflets entire to lobed (19). 



19. Plants from slender elongate roots; umbels axillary or 



terminal; calyx lobes inconspicuous 8. Apium. 



19. Plants from fascicled tuberous or fusiform roots; umbels 



terminal; calyx lobes conspicuous 12. Perideridia. 



12. Ribs of the fruit (some or all of them) prominently winged, the fruit 

 more or less flattened dorsally (20). 



20. Plants annual, with an aniselike odor 17. Anethum. 



20. Plants perennial, without an aniselike odor (21). 



21. Plants hirtellous-pubescent only at base of the umbel. 



24. PSEUDOCYMOPTERUS. 



21. Plants glabrous or pubescent throughout or (in genus Conioseli- 

 num) glabrous except in the inflorescence (22). 

 22. Plants acaulescent or short-caulescent, relatively low, 1 to 55 

 cm. high, subscapose (23). 

 23. Leaf blades narrowly oblong, the leaflets few and remote; 



calyx teeth persistent 23. Pteryxia. 



23. Leaf blades broader, the leaflets many, crowded but usually 

 distinct; calyx teeth rarely persistent (24). 

 24. Lateral ribs winged, the wings thin, the dorsal ribs absent 



or filiform 26. Lomatium. 



24. Lateral and dorsal ribs winged or, if the dorsal ribs obso- 

 lete, then the lateral wings corky (25). 

 25. Calyx teeth conspicuous; leaves pinnate or bipinnate. 



19. Oreoxis. 

 25. Calyx teeth inconspicuous; leaves pinnately decom- 

 pound 22. Cymopterus. 



22. Plants caulescent, mostly tall, 30 to 120 cm. high, the stems 

 more or less leafy (26) . 

 26. Marginal flowers of the umbel with radially enlarged petals; 

 plant tomentose-pubescent; leaves ternate. 



28. Heracleum. 

 26. Marginal flowers regular; plants glabrous or pubescent, never 

 tomentose; leaves pinnate to ternate-pinnate or decom- 

 pound (27). 

 27. Lateral wings corky; leaves decompound, the leaflets 

 narrow, linear-oblong, scabrous-puberulent; stylopo- 



dium absent 25. Leptotaenia. 



27. Lateral wings thin; leaves pinnate to ternate-pinnate, the 

 leaflets broad, lanceolate to ovate, glabrous or puberu- 

 lent; stylopodium present (28). 

 28. Flowers yellow; dorsal ribs filiform, the oil tubes promi- 

 nent on the dorsal surface 27. Pastinaca. 



28. Flowers not yellow; dorsal ribs winged, the oil tubes not 

 prominent on the dorsal surface (29). 

 29. Plants glabrous except for the puberulent inflorescence; 

 stems from a cluster of fleshy roots; ovaries and 



fruit glabrous 20. Conioselinum. 



29. Plants somewhat pubescent; stems from a taproot; 

 ovaries densely hirsutulous, the fruit occasion ally 

 glabrate 21. Angelica. 



1. HYDROCOTYLE. Waterpennywort 



Plants glabrous, perennial, with slender floating or creeping stems 

 or rootstocks; leaf blades round, peltate or nonpeltate; flowers in a 

 simple axillary umbel or an interrupted spike; calyx teeth minute; 

 corolla white, greenish, or yellow; stylopodium depressed to conspic- 

 uously conic; fruit transversely ovate to orbicular, 1 to 3 mm. long, 

 strongly flattened laterally, the ribs slender or obsolete, the oil-bearing 

 cells conspicuous to obsolete, the seed face plane to convex. 



Plants of wet ground, or aquatic. 



