118 



WEED FLORA OP IOWA 



Distribution.— Common in every county in the state of Iowa and 

 east to northeast ; indigenous to the Rocky mountains. 



Extermination. — Easily exterminated by cultivation. 



"Water Hemp {Acnida tuherculata Moq.). 



Description. — A tall, erect annual; leaves lanceolate to rhombic- 

 ovate, acute, or acutish; flowers dioecious; pistillate flowers small, 

 green, clustered in naked or leafy , terminal and axillary spikes ; 

 staminate flowers pale; dehiscent pericarp thin. 



The Acnida ta/mwriscina (Nutt.) Wood, of similar habit. Has 

 circumscissille fruit, otherwise like 'the A. titberculata. 



Distribution. — Common along water courses, prairies and marshes 

 from northeast to Minnesota and Dakota. Found in Iowa in Story, 

 Boone, Polk, Pottawattamie, Woodbury, Emmet, Cerro Gordo, Clin- 

 ton, Linn, Marshall and Allamakee counties. 



Fig. 67. Water Hemp (.Acnida tmberculata) . Common plant with yellowish 



aspect. In old lake beds and prairies. 



(Photographed by Colburn.) 



