352 



WEED FLORA OF IOWA 



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



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

 head ; receptacle flatfish 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 animals, etc. 



Extermination. — 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 (Bidcns 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-corymbose ; 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. 



