BUCKWHEAT FAMILY 403 



Calyx segments not saecate-ililated. 



Leaves obovate or rounded; involucres glandular. . .12. E. pusiUum. 



Leaves reniform; involucres not glandular 13. E. renifornie. 



Outer calyx segments saccate-dilated on each side 14. E. thoijuisii. 



Calyx glabrous. 



Pedicels erect 15. E. thurberi. 



Pedicels not erect. 



Outer calyx segments obovate ; involucres on nodding pedicels. 



Calyx attenuate at base 16. E. cernuum. 



Calyx not attenuate at base 17. E. 7>utans. 



Outer calyx segments cordate at base. 



Involucres on divaricately spreading pedicels 1 to 4 lines long 



18. E. watsotiii. 



Involucres on deflexed pedicels 1 line long or less. . .19. E. defiexum. 



Involucres cylindric or cylindric-turbinate, 5-tootlied, 5 (or 6)-nerved or angled, always sessile, 



solitary or congested in heads; annuals, perennial herbs, or shrubs; mostly deserts or 



dry foothills. — Subgenus OREiiONiUM. 



Involucres solitary, usually scattered. 



Annuals; leaves mostly in a rosette at base. 

 Flowering branches mostly elongated. 



Calyx glabrous; involucres (except the terminal) hugging the branches. 



Plant compactly branching; outer calyx segments fan-shaped with strong- 

 ly incurved sides 20. E. nidularium. 



Plant diffusely or strictly branched. 



Involucres narrowly turbinate, glabrous or nearly so, the teeth 

 prominent. 



Petioles not winged; stems and leaves white-woolly 



21. E. gracile. 

 Petioles conspicuously winged; stems and leaves less tomentose 



22. E. citharaeforme. 

 Involucres cylindric, almost truncate, the teeth minute. 



Stems, leaves and involucres white-woolly 23. E. virgatum. 



Stems glabrous, rarely a little woolly below. 



Involucres 1% to 2X(, lines long 24. E. molestum. 



Involucres ^2 to 1% lines long. 



Involucres 1 to IVi lines long, usually fluted and often 



obscurely constricted a little at tip 



25. E. vimineum. 



Involucres \\. to % line long, not fluted 



26. E. baileyi. 



Calyx densely hairy; involucres spreading a little from the branches 



27. E. dasyanthemum. 

 Flowering branches not elongated. 



Repeatedly and shortly forked; flowers yellow 28. E. mohavense. 



Bearing an irregularly compound umbel 29. E. truiicatum. 



Perennials with densely leafy short woody stems. 

 Inflorescence racemose. 



Leaves roundish, densely imbricated on the caudex 30. E. saxatile. 



Leaves not roundish. 



Involucres scattered on the few elongated branches. 



Involucres scattered, 2 to 3 lines long 31. E. elongatum. 



Involucres scattered or sometimes approximate towards the ends of 



the branches, 1 to \\'-2 lines long 32. E. wrightii. 



Involucres secund and crowded on the short branchlets. .33. E. nodosuvi. 

 Inflorescence cyniose or paniculate. 



Peduncles bearing a divaricately branched panicle. 



Involucral teeth glabrous 34. E. heermannii. 



Involucral teeth pubescent 35. E. plumatella. 



Peduncles bearing corymbose cymes 36. E. microthecum. 



Involucres 2 to several in heaiV!, rarely solitary ; perennials. 

 Calyx-lobes similar or nearly so, nearly equal. 

 Not caespitose. 



Shrubs, at least woody at base; stems very leafy, commonly fascicled. 

 Heads or involucres in a dense compound cyme; insular species. 



