444 THE SMALL GRAINS 



481. Corn cockle or purple cockle (Agrostemma 

 Githago, Linn.). This weed occurs often in wheat fields. 

 The name was given it in England where wheat is often 

 called corn. 



Cockle grows from 1 to 3 feet high, has large purple flowers 

 1^ inches across, and dull black seeds which are roughened by ridges 

 of short spines. 



Wheat screenings from the Northwest are full of cockle. 

 It is very difficult to separate cockle from wheat, the ker- 

 nels of which are near the same size (Fig. 142 d). Special 

 cockle machines are made for the purpose. The seeds are 

 poisonous to animals if eaten, and flour from wheat mixed 

 with cockle is injurious as human food. The poisonous 

 principle is sapotoxin, which affects the digestive tract, 

 causing headache, nausea, and diarrhea. Clean cultiva- 

 tion and crop rotation will eradicate the weed. The 

 seeds of cow cockle (Saponeria Vaccaria, Linn.) are also a 

 frequent impurity in commercial wheat. They are small, 

 however, and readily separated from seed grain. 



482. Wild mustard or charlock (Brassica arwnsis, 

 Kuntze) is one of the best known annual weeds to grain- 

 growers generally. 



It produces erect, branching stems, roughened by short stiff 

 hairs. The flowers are bright yellow. The pods are about l| 

 inches long, and contain reddish brown or black seeds, the size of 

 clover seeds, with which they are consequently commonly found. 

 The seeds are also common in the grain of cereals from which they 

 are readily separated. They will lie in the ground dormant a long 

 time, and then germinate, a fact which makes this weed as bad as 

 some perennials. Bolley (1908, p. 532) found that the seeds will 

 come up well after being buried 4^ years (Fig. 141 /). 



Wild mustard is found in grain fields usually where 

 there is continuous cropping. With clean seed and crop 



