414 Heliantheae 



2. X. Canadense Mill. Stems stout, branched above ; leaves 

 broad-ovoid, slightly lobed, rough-scabrous; Imrs about '2 cm. 

 long, densely beset with stoutish hooked prickles and strongly 

 2-horned at the apex. 



Rather common in low ground, especially in sandy soil. July-October. 



Tribe 5. HELIANTHEAE. Sunflower Tribe. 



Herbs or somewhat shrubby plants with opposite or 

 basal leaves, and commonly balsamic-resinous juice. 

 Rays present, usually showy. Involucral bracts her- 

 baceous or foliaceous. Receptacle chaffy ; chaff sub- 

 tending each flower. Pappus paleaceous, of rigid awns 

 or cup-like, or rarely of rather stout plumose bristles. 

 Rays usually present. 



Rays usually present; pappus paleaceous. 



Involucral bracts imbricated in several series. 

 Rays sterile. 



Achenes quadrangular-compressed, glabrous. 29. HELIANTHUS. 

 Achenes flattened, villous, cilate on the margins. 30. Encelia. 

 Rays fertile 31. Verbesina. 



Involucral bracts of 2 dissimilar series. 



Rays present, fertile. 38. LEPTOSYNE. 



Rays sterile or none. 33. BlDENS. 



Rays wanting; pappus of plumose bristles. 3-1. BEBBTA. 



29. HELIANTHUS L. SUNFLOWER. 



Im - cc1 annual or perennial herbs, with opposite or 

 alternate simple leaves, and large peduncled corymbose 

 or military heads of both tubular and ray-flowers, the 

 rays yellow, the disk yellow brown or purple, [nvolu- 

 cre hemispheric or depressed, its bracts imbricated in 

 several series. Receptacle Hat, convex or conic, chaffy, 

 the chaff subentire. Ray-flowers sterile. Disk-flowers 

 perfect, with short tube and 5-lobed Limb. Style-branches 

 tipped with hirsute appendages. Achenes thick, oblong 

 or obovate, compressed or somewh.it 4-angled. Pappus 

 of 2 scales or awns, or sometimes with "J-l additional 

 shorter ones, deciduous. 



