DISPERSAL OF WEED SEEDS 23 



were found night-flowering catchfly, corn cockle, and bull 

 thistle. 



Grain Seed. The wild oats is frequently scattered 

 with oats, but there is little of this weed in Iowa except 

 in a few counties in northern and northwestern parts. 

 Mustard is also frequently scattered with oats. There is some 

 danger of scattering quack grass seed with oats. Quack 

 grass seed found maturing with oats will germinate. In 

 one case 8 per cent, of the seed was capable of producing 

 new plants. In an investigation of quack grass in north- 

 ern Iowa and Minnesota it was found that it is nearly 

 always scattered near the grain elevators. Straw is an 



Fig. 19. Seeds distributed with wheat seed; a and b, wheat; d and e, 

 cockle; c, common chess. (U. S. Dept. Agrl.) 



important factor in scattering quack grass. A single 

 farm has been responsible for scattering quack grass along 

 the highway in every direction leading from the farm. 

 The straw, with its seed of quack grass, fell along the 

 roadside, and in a few years quack grass, was observed 

 along the highway. One farmer said the quack grass 

 was introduced on his farm by using oat straw for cover- 

 ing his grapes. Many other similar cases, are on record. 

 Cockle, cowherb and vetch are frequently scattered with 

 wheat seed. 



Garden Seed and Ornamental Plants. Shoofly, which 

 has been widely cultivated as an ornamental plant in this 

 state, has scattered to the fields and has become a 

 troublesome weed in grain fields. Mexican fireweed, 



