FLORA OF THE DISTRICT OF COLUMBIA. 289 



1. Bidens laevis (L.) B. S. P. Bur marigold. 

 Wet ground; occasional. Sept. Eastern U, S. (B. lugens Greene; B. chrysanthe- 



moides Michx.) 



2. Bidens cernua L. Bur marigold. 

 Wet ground; common. Aug. -Oct. Nearly throughout the U. S. and southern 



Can. ; also in Eur. and Asia. 



6. Bidens bidentoides (Nutt.) Britton. Swamp beggar-ticks. 



Wet ground; near Cabin John. Aug. -Sept. N, J. to Md. 



4. Bidens connata Muhl. 



Swamp near Hyattsville. Sept. Eastern U. S. 



5. Bidens comosa (A. Gray) Wiegand. 



Swamps or wet ground; common, Aug. -Sept. Eastern U. S. 



6. Bidens aristosa (Michx.) Britton. 



Wet ground along the Potomac, and at Chesapeake Junction. Aug. -Sept. East- 

 ern U. S. 



7. Bidens bipinnata L. Spanish needles. 

 Woods; common. Sept. -Oct. Eastern U. S., west to Ariz. 



8. Bidens vulgata Greene. 



Woods; frequent. Aug, -Oct. Widely distributed in N. Amer. 



9. Bidens discoidea (Torr. & Gray) Britton. 



Holmead Swamp and Bennings. Sept. Eastern U. S. (Coreopsis discoidea Torr. 

 AGray.) 



10. Bidens frondosa L. Beggar-ticks. 

 Damp woods or fields; common. Aug.^Oct. Nearly throughout the U. S. and 



southern Can. 



35. GALINSOGA Ruiz & Pav. 



Rays reddish; pappus of the disk flowers about half as long as the achenes. Pubescence 



copious, of loose spreading hairs 1. G. caracasana. 



Rays white; pappus of the disk flowers about as long as the achenes. 

 Pappus scales of the disk flowers rather obtuse ; pubescence of somewhat appressed 



hairs 2. G. parviflora . 



Pappus scales of the disk flowers very acute, bristle-tipped; pubescence of loose 

 and spreading hairs 2a. G. parviflora hispida. 



1. Galinsoga caracasana (DC.) Schultz Bip. 



In a cornfield along the Potomac near Great Falls, August 7, 1910 (F. W. Pennell). 

 Native of tropical Amer.; reported as adventive in Md. and N. J. 



2. Galinsoga parviflora Cav. 



Waste ground and cultivated fields; frequent. June-Oct. Native of tropical 

 Amer. ; adventive in many parts of the U. S. 

 2a. Galinsoga parviflora hispida DC. 



Waste ground about Washington and in fields near Great Falls. Aug. -Oct. Na- 

 tive of tropical Amer.; adventive in the eastern U. S. 



36. HELENIXTM L. 



Disk of the heads yellow; leaves elliptic-lanceolate to ovate-lanceolate, toothed. 



1. H. autumnale. 

 Disk purple; leaves lanceolate or linear-lanceolate, usually entire. 



2. H. nudiflorum. 



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