380 ASTERACEAE. 



1. X. spinosum L. Widely branching from the base, about 

 6 dm, high; leaves ovate-lanceolate, more or less lobed or pinnatifid, 

 glabrate and green above, white-tomentose beneath; axils each 

 with a short-stalked sponged yellow spine about 2 cm. long; burs 

 about 10 mm. long, armed with short weak prickles. 



Frequent along roadsides and in waste places. August-October. 



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

 broad-ovoid, slightly lobed, rough-scabrous; burs 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 Trtbe. 



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, gla- 



30. HELIANTHUS L. Sunflower. 



Erect annual or perennial herbs, with opposite or 

 alternate simple leaves, and large peduncled corymbose 

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

 rays yellow, the disk yellow brown or purple. Involucre 

 hemispheric or depressed, its bracts imbricated in several 

 series. Receptacle fiat, 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 



