Flora of Denver. 25 



igg. Helianthus Maximilian! SCHRAD. Stem very tall 

 and rough, leaves thick, lanceolate, sparingly serrate, usually 

 keeled, flowering branches at the top of the stem. North Den- 

 ver recently introduced. 



200. Verbesina encelioides CAV. Usually branching, 

 leaves ovate, unevenly serrate, canescent; rays 3-cleft, akenes 

 flat, broadly winged. Introduced within six years, very com- 

 mon especially in North Denver. Summer and fall. 



201. Coreopsis tinctoria NUTT. Usually tall and branched 

 above. Yellow rays brown near the base, disk dark. Rather 

 rare. Along the Platte. Summer. 



202. Bidens frondo"sa L. (STICK-TIGHT.) Heads rayless, 

 akenes hairy 2-awned. Along the ditches, common, late sum- 

 mer and fall. 



203. Bidens cernua L. Heads nodding after the rays 

 have withered. Summer and fall. In marshy places along 

 the Platte. 



204. Bidens chrysanthemoides MICHX. (BUR-MARIGOLD.) 

 Heads large with conspicuous rays not nodding. Common 

 along the ditches. Fall. 



205. Bidens tenuisecta GRAY. (SPANISH-NEEDLES.) 

 Leaves pinnately dissected into narrow divisions, rays yellow, 

 longer than the disk, akenes smooth 2-awned. Along the 

 ditches, late summer. 



206. Thelesperma ambiguum GRAY. Diffusely branch- 

 ing, a foot high, flowers numerous, rays yellow, disk yellow, 

 divisions of the leaves narrowly linear. This is usually called 

 Coreopsis and is common around Denver. Summer. 



207. Thelesperma gracile GRAY. Tall, opposite leaves 

 scattered, heads rayless, disk yellow turning darker. North 

 Denver. Summer. 



