BUCKWHEAT FAMILY 21 



Calyx-lobes similar, not concave, rounded at the apex, glabrous. 



20. E. gracillimum. 



Calyx-lobes dissimilar, the outer deeply concave and clawed, glandular-puberulent. 



21. E. angulosum. 



Flowers concealed by the conspicuous cotton-like tomentum of the inner surface of involucre 

 and bractlets. 22. E. gossypinum. 



Plants pilose; leaves linear, revolute; involucre less than 1 mm. long. 23. E. spergulinum. 

 Stem leaves all reduced to bracts, or those of first node sometimes foliaceous. 

 Leaves all basal, often pilose but never tomentose. 

 Calyx pubescent with hooked hairs. 



Branches not widely divergent; achenes distinctly exserted. 24. E. hirtiflorum. 



Branches widely divergent; achenes not exserted or obscurely so. 25. E. inerme. 

 Calyx hispidulose or puberulent, the hairs not hooked. 



Calyx-lobes notched and apiculate at apex; leaves oblanceolate or obovate. 



26. E. apiculatum. 



Calyx-lobes obtuse or acutish, not apiculate. 



Leaves spatulate; calyx rose-colored, minutely puberulent. 27. E. Parishii. 



Leaves rounded, often cordate; calyx yellow, hispidulose. 28. E. trichopes. 



Leaves basal and often at the first node, thinly tomentose on the lower surface, also on the lower portion 

 of the stem; calyx pubescent. 29. E. Ordi:. 



tnvolucres S-lobed or 5-toothed. 



Leaves all basal, mostly rounded or reniform. 

 Leaves pilose or hirsute, never tomentose. 



Calyx conspicuously pubescent on the outer surface; stem often inflated. 



30. E. inflatum. 



Calyx glabrous; stem not inflated. 31. E. esmeraldense. 



Leaves white-woolly at least beneath. 



Calyx pubescent or glandular-puberulent on the outer surface, at least toward the base. 

 Outer calyx-lobes saccate on either side of the cordate base. 32. E. Thomasii. 



Outer calyx-lobes neither saccate nor cordate at base. 

 Involucre glandular-pubescent. 



Calyx glandular-puberulent only at base, the outer lobes rounded and abruptly nar- 

 rowed to a short claw. 33. E. Thurberi. 

 Calyx glandular-puberulent throughout on the outer surface, the outer lobes oblong- 

 spatulate in age. 34. E. pusillum. 



Involucre glabrous; calyx glandular-puberulent on the outer surface. 



35. E. reniforme. 

 Calyx glabrous. 



Peduncles filiform; outer calyx-lobes obovate or quadrate not cordate at base. 



36. E. cernuum. 



Peduncles stouter; outer calyx-lobes elliptic-ovate or round ovate, cordate at base. 



37. E. deftexum. 

 Leaves basal and also on the first and second nodes of the stem. 



Plants glabrous except for a thin arachnoid tomentum on lower surface of leaves; calyx glabrous. 



38. E. argillosum. 



Plants densely white-tomentose throughout; calyx-lobes papillose on the outer surface. 



39. E. vestitum. 



III. Oregonium 



Annuals, perennials or low shrubs, some glabrous but many of the species more or 

 less white-tomentose. Bracts ternate, connate at base, seldom foliaceous, usually short 

 and acute and more or less rigid. Involucres cylindric-turbinate or prismatic, erect, 

 5-6-veined, with as many short erect teeth, sessile or rarely subsessile in the axils of the 

 bracts, clustered in heads, or scattered along the virgate branches or in racemes or cymes. 

 Calyx rather abruptly contracted at base, not becoming attenuate in age (except in cro- 

 catum and saxatile) ; ovary and filaments mostly glabrous, the latter sometimes hairy at 

 base. 



Involucres solitary at the nodes, the lateral ones appressed to the branchlets. 



Annuals. 



Calyx-lobes fan-shaped, their sides incurved below the broad truncate apex. 40. E. nidularium. 



Calyx-lobes not fan-shaped. 



Calyx conspicuously villous-pubescent. 41. E. dasyanthemum. 



Calyx not villous-pubescent. 



Outer surface of calyx puberulent or glandular-puberulent. 



Involucre turbinate; stems densely white-tomentose at base; flowers rose-colored. 



42. E. elegans. 



Involucre cylindric; flowers yellow or white. 43. E. Baileyi. 



Outer surface of calyx glabrous or rarely minutely puberulent at base in vimineum and 

 Covilleanutn. 



Involucre scarcely 1 mm. long; calyx 0.7 mm. long, pale yellow. 



44. E. brachyanthum. 



Involucre about 2 mm. or more in length; calyx over 1 mm. long. 



Inflorescence with elongated virgate branchlets, bearing involucres at the nodes, the 

 lateral ones appressed. 

 Leaves oblong-obovate to oblanceolate; whole plant more or less densely tomentose. 



Involucres 3 mm. long; flowers yellow, rarely tinged with rose. 



45. E. inrgatum 



Involucres 1.5-2 mm. long; flowers white (sometimes yellow), often with 

 the mtdvein of the lobes rose-colored. 



