184 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Perennials. 



Perianth narrowed into a long stipelike base, pubescent. 



Perianth whitish; styles hairy at least to the middle 18. E. jamesii. 



Perianth bright yellow; styles hairy only at the base 19. E. bakeri. 



Perianth not narrowed into a stipelike base, pubescent or 

 glabrous. 

 Ovaries and fruit pubescent. 



Stems leafy; perianth 6 mm. long 20. E. longifolium. 



Stems not leafy, scapelike; perianth 3 mm. long or less. 

 Inflorescence an open cyme 10 to 15 cm. high; • 



involucres 2 mm. high 21. E. leucophyllum. 



Inflorescence a congested cyme less than 3 cm. 



high; involucres 3 to 5 mm. high 22. E. lachnogynum. 



Ovaries and fruit glabrous or nearly so. 



Involucres in a headlike cluster 23. E. ovalifolium. 



Involucres in open cymes. 

 Cymes one-sided and spikelike. 

 Leaves basal, abruptly narrowed at the base or 



subcordate; perianth 5 mm. long 24. E. racemosum. 



Leaves scattered along the woody branches, 



tapering at the base; perianth 3 mm. long 25. E. wrightii. 



Cymes dichotomous or trichotomous. 

 Perianth deep dark red; stems and involucres 



glabrous; plants tall and stout 26. E. atrorubens. 



Perianth white, pink, or yellow, never dark red; 

 stems and involucres glabrous or pubescent; 

 plants various. 

 Perianth densely sericeous. 



Leaves elliptic, acute, tomentose 27. E. havardii. 



.Leaves orbicular, obtuse, not tomentose 28. E. infiatum. 



Perianth glabrous. 

 Perianth bright yellow; leaves glabrous (all 



basal, orbicular or broadly ovate) 29. E. gypsophilum. 



Perianth white or pink; leaves tomentose, at 

 least beneath. 

 Leaves all basal, orbicular or obovate, the 

 stems densely cespitose; leaves per- 

 manently and densely white-tomentose 



on the upper surface 30. E. tenellum. 



At least the lower part of the stem leafy; 

 stems usually not densely cespitose; 

 leaves glabrate on the upper surface. 

 Flowering branches leafy for only a few 

 centimeters at the base, the pedun- 

 cles relatively long. 

 Stems and involucres tomentulose 

 throughout; lobes of the involucre 

 acute; leaves narrowly oblong, 



flat 31. E. ainsliei. 



Branches of the inflorescence and in- 

 volucres glabrous; lobes of the 

 involucre broadly obtuse; leaves 

 various. 



