352 



WEED FLORA OF IOWA 



Fig. 205-A. Distribution of Boot-jack. 



lucre double, the outer foliaceous; bracts ciliate, longer than the 

 head; receptacle flattish with deciduous chaff; achenes narrowly 

 acuminate, 2-awned, the awns downwardly barbed. 



Distribution. — ^Widely distributed in moist places throughout 

 the northern states ; often a very troublesome weed in gardens. It 

 is widely scattered because of the "seeds" adhering to clothing, 

 pelts of aijimals, etc. 



Extermvnation. — Boot-jack is easily exterminated by cultivation. 

 The weed is disseminated- by animals and man. It would be well 

 to cut off the plant close to the surface of the ground when in 

 flower. 



Tickseed {Bidens aristosa (Michx.) Britton). 



Description. — A smoothish, slightly pubescent, annual 2-4 feet 

 high ; leaves 1-2-pinnately, 5-7-divided, petioled ; leaflets lanceolate, 

 cut-toothed or pinnatifid; heads panicled-eorymbose ; scales of the 

 involucre in 2 series, the outer about as long as the inner, ciliate; 

 ray flowers conspicuous, yellow; achenes obovate with ciliate mar- 

 gins, usually with 2 divergent teeth ; a somewhat showy plant with 

 yellow flowers. 



Distribution. — From Michigan and southern Iowa to Kansas 

 and Texas. Abundant in Missouri; probably indigenous to south- 

 ern Iowa; in recent years has made its appearance in Wapello, 

 (Pammel) Marion, (Pammel) Polk (Bakke) and Decatur (Ander- 

 son) counties. 



