DESCRIPTIVE MANUAL 



197 



Fig. 11 3- A. Distribution of Wild Liquorice. 



ported from the Great Lakes; commonly reported from Story, 

 Greene, Pottawattamie, Harrison, Monona, Fremont, and Decatur 

 counties. 



Extermination. — This perennial plant whose burs resemble the 

 cocklebur is easily exterminated by cultivation. Do not permit the 

 seeds to mature. Cut off the plants at the surface of the ground 

 to prevent flowering, if they occur in the pasture or meadow. 

 Where the land can be cultivated, give the ordinary plowing, fol- 

 lowed with harrowing to bring the roots to the surface so they are 

 exposed to the sun. A few days' exposure to the sun will kill them. 



Common Vetch (Vicia sativa L.). 



Description. — A smooth or slightly pubescent annual from 1-2V2 

 ft. high with simple stem ; leaflets 5-7 pairs, obovate-oblong to lin- 

 ear, notched or mucronate at the tip ; 1 or 2 nearly sessile flowers 

 borne in the axils of the leaves, corolla violet-purple; pod linear, 

 several-seeded, seeds black. 



Distribution. — This weed has long been known as troublesome in 

 the grain fields of Europe, and in the northern states. It is particu- 

 larly abundant in northeastern and northwestern Iowa and in some 

 of the grain growing sections of the southern part of the state. 



Extermination. — Clean seed sown in clean soil is the only method 

 of displacing the weed. 



