982 Compositae Bidens 



Leaves all simple, sometimes the median and basal ones cleft or 3-parted but, if 

 parted, the terminal segment not petiolate. 

 Rays large and showy, longer than the disk; heads somewhat nodding at anthesis; 

 stamens exserted. 

 Stem erect, rarely decumbent, usually somewhat hispid at least on the lower inter- 

 nodes; leaves connate at the base; outer bracts of heads unequal; rays wanting 

 or less than 1.7 cm long; chaff with a yellow tip; margins of achenes pale. 



1. B. cernua. 



Stem decumbent at the base and often floating, smooth; leaves sessile; outer 

 bracts subequal, rarely exceeding the disk; rays 1.5-3 cm long; chaff reddish 

 brown at the tip; margins of achenes not pale. (See excluded species no. 



673, p. 1102) B. laevis. 



Rays scarcely exceeding the disk or wanting; heads erect; stamens included or 

 exserted. 

 Stamens included; disk-flowers pale yellow, 4-toothed; corollas yellowish green; 



inner mature achenes mostly 7-8 mm long, usually 3-awned 2. B. comosa. 



Stamens exserted; disk-flowers orange yellow, 5-toothed; inner mature achenes 

 mostly about 6 mm long, the outer 3-awned, the inner 4-awned. 

 Primary cauline leaves 3-lobed, the remaining ones usually not lobed, sub- 

 sessile or with short, margined petioles 3. B. connata. 



Primary cauline leaves simple, as are all the other leaves, rarely a cauline 



leaf lobed; petioles usually long and scarcely margined 



3a. B. connata var. petiolata. 



Leaves pinnate. 



Inner mature achenes 12-18 mm long, 4-angled, somewhat quadrangular, narrowed 



at the top; awns 4, with retrorse barbs 4. B. bipinnata. 



Inner mature achenes not as above. 



Achenes with upwardly barbed or hispid awns or bidentate with the sides of the 

 achenes upwardly pubescent. 

 Outer involucral bracts 3-5, generally 4, glabrous or nearly so; heads small; 

 rays wanting; inner mature achenes 1-1.5 mm wide; awns mostly 1-2 mm 



long 5. B. discoidea. 



Outer involucral bracts generally 8 or more, ciliate or hispid; rays showy, 

 usually about twice as long as the head. 

 Inner mature achenes 1-2 mm wide, usually about 1.5 mm wide; awns gen- 

 erally 0.5-3 mm long 6. B. coronata. 



Inner mature achenes generally 2.5-3.5 mm wide. 



Awns generally 2.5-4 mm long 1. B. aristosa. 



Awns mere teeth, usually about 0.5 mm long 7b. B. aristosa var. mutica. 



Achenes with downwardly barbed awns. 



Rays small, inconspicuous; outer bracts mostly spatulate, the larger ones gen- 

 erally 1.5-3 mm wide, ciliate but not hispid. 

 Outer involucral bracts 6-8; inner mature achenes 6-9.5 mm long, 2-2.75 mm 



wide; awns 3-5.5 mm long, generally 3-4 mm long 8. B. frondosa. 



Outer involucral bracts 10-16, foliaceous, longer and wider than in the pre- 

 ceding; inner mature achenes mostly 8-12 mm long; awns generally 



4-5.5 mm long 9. B. vulgata. 



Rays conspicuous, generally twice as long as the disk; outer involucral bracts 

 linear, or very narrow and widest below the middle, all generally less than 

 1.5 mm wide, densely hispid. 



Outer involucral bracts 8-10, ciliate, shorter than the inner bracts 



7a. B. aristosa var. Fritcheyi. 



Outer involucral bracts 12-20, coarsely hispid, mostly longer than the inner 

 bracts 10. B. polylepis var. retrorsa. 



1. Bidens cernua L. Nodding Bur-marigold. Map 2148. More or less 

 frequent in the northern part of the state and becoming infrequent to rare 



