494 



COMPOSITAE. 



VOL. III. 



13. Coreopsis rosea Xutt. Small Rose or Pink Tickseed. Fig. 4504. 



Coreopsis rosea Nutt. Gen. 2: 179. 1818. 



Perennial by slender rootstocks; stems at length 

 much branched, slender, strict, glabrous, 6'-24' high. 

 Leaves opposite, linear, glabrous, entire, obscurely i- 

 nerved, i'-2i' long, i"-i" wide, sessile, or the lower 

 petioled ; heads slender-peduncled, several or numer- 

 ous, 6"-i2" broad ; disk yellow ; rays 4-8, pink or rose- 

 colored (occasionally white), oblong to obovate, slight- 

 ly 3-toothed or sometimes entire ; inner bracts of the 

 hemispheric involucre ovate-oblong, acutish or obtuse, 

 glabrous, much longer than the lanceolate outer ones ; 

 achenes oblong or linear-oblong, thin, not winged, 

 nearly straight, slightly ribbed on the inner face; pap- 

 pus a very short truncate crown. 



In open swamps, eastern Massachusetts to Georgia, near 

 the coast. July-Aug. 



71. BIDENS L. Sp. PI. 831. 1753. 



Annual or perennial herbs, with opposite serrate lobed divided or dissected leaves, or the 

 uppermost alternate, and mostly large heads of both tubular and radiate flowers, or the rays 

 none, or rudimentary. Involucre campanulate or hemispheric, its bracts in 2 series, distinct, 

 or slightly united at the base; the outer often foliaceous and much larger than the inner. 

 Receptacle flat or nearly so, chaffy, the chaff subtending the disk-flowers. Rays, when present, 

 neutral, mostly entire, yellow in our species. Disk-flowers perfect, fertile, their corollas tubu- 

 lar, 5-toothed. Anthers entire, or minutely sagittate at the base. Style-branches with short 

 or subulate tips. Achenes flat, or quadrangular, cuneate, oblong or linear, the outer ones 

 often shorter than the inner. Pappus of 2-6 teeth or subulate awns, upwardly or down- 

 wardly barbed or hispid. [Latin, two-toothed, referring to the achenes.] 



About 75 species of wide geographic distribution. Besides the following, about 12 others occur 

 in the southern and southwestern United States. Type species : Bidens tripartite, L. 



Leaves lanceolate, serrate, undivided, rarely 3~5-lobed or incised. 

 Rays present, large and conspicuous. 



Rays large, longer than the involucral bracts. 

 Rays short, rarely as long as the involucral bracts. 

 Rays rudimentary, or none. 



Heads nodding after flowering. 

 Heads persistently erect. 



Pappus awns downwardly barbed. 



Involucral bracts not foliaceous ; stem purple ; flowers orange. 

 Involucral bracts foliaceous ; stem straw-color ; flowers greenish 



Pappus awns upwardly barbed ; involucre narrow. 

 Leaves, some or all of them, pinnately i-3-parted or dissected. 

 Rays rudimentary, or none, or very short. 



Achenes flat ; leaves, some or all of them, i-3-divided. 



Outer involucral bracts 4-8 ; achenes black or nearly black. 

 Leaves membranous ; heads 2" 3" high ; awns short. 

 Leaves not membranous; heads s"-7" high; awns long. 

 Outer involucral bracts 10-16; achenes brown. 

 Achenes linear ; leaves dissected. 

 Rays large and conspicuous. 



Achenes sparingly pubescent, not ciliate ; pappus of 2 short teeth. 

 Achenes ciliate ; pappus 2-4 subulate teeth or awns. 

 Achenes cuneate, or linear-cuneate. 

 Achenes obovate, very flat. 



Bracts of the involucre glabrous, or ciliate, short. 

 Outer bracts densely hispid, much longer than the inner. 



1. B. laevis. 



2. B. cernua. 



2. B. cernua. 



3. B. connata. 

 yellow. 



4. B. comosa. 



5. B. bidentoides. 



6. B. discoidea. 



7. B. frondosa. 



8. B. vulgata. 



9. B. bipinnata. 



10. B. coronata. 



11. B.trichosperma. 



12. B. aristosa. 



13. B. involucrata. 



