COMPOSITE FAMILY 



COMPOSITAE 



TICKSEED SUNFLOWER. SWAMP MARIGOLD 



Bidens trichosperma (Michx.) Britton 



Thirteen species of Bidens are known to occur in Illinois 

 and some of them are very similar and equally difficult to dis- 

 tinguish. The genus is always identified by the persistent 



pappus of 2 or more awns either up- 

 wardly or downwardly barbed, but 

 only extremely detailed study will 

 disclose the differences between 

 species within groups of similar-ap- 

 pearing flowers. 



They go by various names, such 

 as Sticktight, Spanish Needles, De- 

 vil's Pitchforks, Beggar Ticks, Tick- 

 seed and Bur Marigold. In some 

 species the ray flowers are very in- 

 conspicuous or absent, whereas in 

 others, like the one illustrated, the 

 rays are very showy. All bloom dur- 

 ing the latter part of the season, 

 from July or August to late autumn. 



The Tickseed Sunflower is one of 

 the commonest and most showy 

 Bide7js. Often in September great 

 areas ot wet land, marshes and low 

 meadows from Massachusetts to 

 Georgia, Kentucky, Illinois and 

 Michigan are solid sheets of golden 

 bloom of this or a closely related 

 species. 



The stem is 2-5 feet high, much branched and smooth. The 

 bracts of the involucre are in 2 series, the outer ones narrower 

 than the inner. The receptacle is flat and chaff"y. Ray and disk 

 flowers are yellow. The pappus is 2 upwardly barbed awns. 



The Southern Tickseed Sunflower, Bidens voronata (h.) Fisch.. and 

 the Western Tickseed Sunflower. Bidens aristosa (Michx.) Britton. are 

 considerably alike but the most noticeable difference is the hairy stems 

 of the latter. The leaves of B. coronata are r>-divided, the tormina! 

 division much larger anr toothed or lobed. Those of the western 

 plant are .5-7 divided and the segments are toothed, cut lolled or 

 deeply divided. The upper leaves of both are small and may be un- 

 divided or merely lobed. The heads of yellow flowers are 1-2 inches in 

 diameter in both species but in the southern the outer bracts of the 

 involucre are lojiger than the inner, whereas in the western sunflower 

 they are not. The pappus of B. oristosa is 2. rarely 4. slender up- 

 wardly or downwardly barbed awns sometimes as long as the mar- 

 ginally fringed akene. In B. coronata it is 2 blunt and spreading teeth 

 on the sparingly hairy but not fringed akene. 



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