Phytologia (A ug 2004) 86(2) 8 1 



20. Stems variously procumbent to erect, the plants 

 often divaricately-branched, shrubby, and up to 2 m 

 high; achenes often heteromorphic, those of the 

 ray and disk winged or not; Pacific slopes and 

 central Ver southwards (21) 



21. Leaves elliptic to lance-linear, sessile or nearly so; 



Pacific slopes, Nay, Jal W. vexata 



21. Leaves ovate to lanceolate, clearly petiolate (22a) 



22a. Perennials; ray corollas bright yellow, the 



ligules mostly 5 mm long or more; widespread W. scabra 



22a. Annuals with slender tap-roots; ray corollas pale 



yellow to white, the ligules 1-5 mm long; Jal, Cps (22b) 



22b. Leaves lanceolate; disk florets mostly sterile; Jal W. elottiana 



22b. Leaves oval to ovate; disk florets mostly fertile; Cps W. iners 



23(19). Erect, coarse, suffruticose, shrubs or shrublets 



mostly 1-2 m high; Ver, Oax, Cps (Isthmus of 



Tehuantepec) W. tehuantepecana 



23. Perennial herbs or suffruticose shrublets 0.2-0.9 m 



high; Son to Hid northwards (24) 



24. Stems stiffly erect, suffruticose, becoming a 



bushy shrublet; leaves commonly lacerately- 



lobed at the base; widespread, e Chi, Coa, Nue, 



Tarn to Mex W. hispida 



24. Stems procumbent, recumbent, or erect suffruticose 



herbs; leaves mostly ovate and evenly serrate; 



Son, w Chi, Pacific slopes (25) 



25. Leaves mostly 2.5-6.0(8.0) cm long; herbs 30-60 cm 



high; w Chi and adjacent Son W. chihuahuana 



25. Leaves mostly 6-12 cm long; shrubs or shrublets to 



1.5 m high; Pacific Slopes, Jal to Gue W. strigosa 



