SUNFLOWER FAMILY. 407 



Tribe 6. Madieae. Tarweed Tribe. 



Ours annuals (except one species of no. 45 and no. 54). Herbage glandular, 

 viscid or heavy-scented (except nos. 53, 54, and 55). Leaves alternate or 

 opposite. Bracts of the involucre in a single series, each partly or completely 

 enclosing an achene. Bracts of the receptacle commonly in a single series 

 between disk- and ray-flowers and often united into a cup, or sometimes 

 scattered among the disk-flowers. Kays always present, showy or inconspicuous. 

 Anthers not caudate. Kay-achenes always fertile, without pappus (except nos. 

 51 and 54) ; disk-achenes fertile or sterile, their pappus paleaceous, awn-like 

 or none. 



A. Ray-achcncs laterally compressed, completely enfolded by the deeply sulcate bracts of 



the involucre which are strongly carinate on the back. 



Rays showy or inconspicuous; disk-flowers few to many; mostly tall plants 45. Madia. 



Rays inconspicuous; disk-flowers one; low slender plants 46. Harpaecarpus. 



B. Ray-achenes turgid or somewhat obcomprcssed, half enclosed by the bracts of the 



involucre which are rounded on the back. 



Achenes of ray without pappus. 



Rays 5 to 40, 2 or 3-lobed or -toothed; disk-achenes with or without pappus; leaves, 

 at least at base, not entire. 

 Leaves not spiny, commonly viscid and glandular. 



Receptacle flat; rays 5 to 25, always (?) 3-lobed; bracts of involucre and of 



receptacle at length deciduous 47. Hemizonia. 



Receptacle convex; rays about 15, 3-lobed; bracts of involucre and of receptacle 



persistent, the outer beset with clavate processes 48. Holocarpha. 



Leaves (at least the upper) spinose and rigid, little viscid or glandular; rays 25 to 

 40, 2-lobed; bracts of involucre and of receptacle persistent or deciduous, not 



beset with processes 49. Centromadia. 



Rays 1 to 5 (or 8), broad and palmately 3-lobed; achenes with paleaceous pappus; 



leaves all narrowly linear and entire 50. Calycadenia. 



Achenes of ray with pappus; disk-achenes with plumose pappus 51. Blepharizonia. 



C. Ray-achenes obcomprcssed or clavate, completely enfolded by the bracts of the involucre, 



which at base have thin margins and Aattish backs. 

 Achenes in fruit not expanding; pappus present or none. 



Vernal annuals; rays 8 to 20, commonly showy, yellow, white, or yellow tipped with 



white 52. Layia. 



Summer plants; rays 5, comparatively inconspicuous. 



Annuals; heads clustered; bracts of receptacle distinct; rays pale yellow; pappus 



none 53. Lagophylla. 



Perennial; heads solitary; bracts of receptacle connate; flowers white or rose-tinged; 



pappus present 54. Holozonia. 



Achenes in fruit expanding into an open globose head; pappus silvery-scarious, the longer 

 set of paleae longer than the achenes 55. Achyrachaena. 



Tribe 7. Heliantheae. Sunflower Tribe. 



Herbs with mostly opposite or radical leaves. Herbage commonly with bal- 

 samic-resinous juice. Rays present, almost always showy. Bracts of the invol- 

 ucre herbaceous or foliaceous, or at least not scarious. Receptacle with chaff- 

 like bracts, each subtending a flower. Anthers not caudate. Pappus paleaceous, 

 of rigid awns, or cup-like, never of capillary bristles. Achenes thick or flat- 

 tened contrary to the subtending chaffy bract, never parallel with it. 

 A. Bracts of the involucre in 2 to several series. 



Involucre of 2 series of similar bracts; flowers white; leaves opposite 56. Eclipta. 



Involucre imbricated, its bracts in several series; flowers yellow. 



Ray-flowers maturing achenes; low perennials with broad radical leaves. 



Pappus none 57. Balsamorrhiza. 



Pappus present 58. Wyethia. 



Ray-flowers not maturing achenes. 



Pappus persistent; achenes thick, not notched at summit; leaves alternate, except 

 the lowest; tall annuals or perennials 59. Helianthus. 



