232 UNIVERSITY OF MISSOURI STUDIES [3^4 



980. A. triflda L. Giant ragweed. 



Very common in alluvial flats and waste grounds. 

 Quebec to the Northwest Territory; Florida to Ar- 

 kansas and Colorado. 



981. A. integrifolia Muhl. [A. trifida integrifolia (Muhl.) 

 T. & G.]. 



Occasional in poor soil. 



New York to Michigan and Illinois; Virginia to Col- 

 orado. 



982. A. artemisiaefolia L. Common ragweed. 

 Abundant in fields and waste grounds. 



Nova Scotia to British Columbia; Florida to Mexico; 

 West Indies: South America: naturalized in Europe. 



983. A. psilostachya DC. Western ragweed. 



Along the Wabash railroad north of Columbia, and along 

 highways west. 



Michigan to the Northwest Territory; Missouri and 

 Texas to California and Mexico. 



406. XANTHIUM L. Clotbur. 



984. X. glabratum (DC.) Britton {X. strmnarium Auct.]. 

 Common cocklebur. 



Waste places and low grounds. 



New England to Nebraska; Florida to Mexico. 



985. X. Pennsylvanioum Wallr. Pennsylvania cockle- 

 bur. 



Common in waste places and along streams. 

 Ontario to Minnesota; District of Columbia to Arkan- 

 sas. 



986. X. speciosum Kearney. Great cocklebur. 

 Waste places and along streams. 



Missouri to North Dakota; Tennessee to Texas. 



987. X. commune Britton. Common clotbur. 

 Common in waste places. 



Quebec and New York to Kansas; Missouri to Arizona. 



