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WEED FLORA OF IOWA 



Fig. 192. Perennial Ragweed (Ambrosia pailostachya) . 



roadsides. 

 (Photographed by Quade. ) 



Pastures, drift soils. 



Marsh Elder (Iva xantliifolia Nutt.), 



Description. — An annual 1-8 ft. high ; stem frequently pubescent 

 when young ; leaves opposite, rhombic, ovate, or lowest heart-shaped, 

 doubly serrate, or cut-toothed, obscurely lobed ; upper surface 

 minutely scabrous, canescent beneath, especially when young; 

 petiole frequently ciliate at its upper end ; flowers borne in spikelike 

 clusters forming a compound panicle; heads small, crowded; outer 

 bracts of the involucre broadly ovate, greenish ; inner membrana- 

 ceous ; achenes glabrate. This plant is also known botanically as 

 Cyclachaena xanthifolia Fr. 



Distribution. — Common in the eastern Kockies, to Saskatchewan 

 and western Wisconsin, most abundant in Iowa along Missouri 

 river where it is troublesome in fields, along highways, and in 



