DISEASES OF WHEAtf 153 



it is mistaken for chess. It is an annual grass, and can be 

 cleaned from seed wheat by the chess method. 



Cockle (Agrostemma githago L.) is a member of the pink 

 family and a widely distributed weed of the wheat fields since 

 ancient times. In size and weight its seeds resemble wheat 

 grains so closely as to be removed with difficulty. They are 

 easily seen in the grain, however, and are injurious to flour, 

 consequently they render wheat less marketable. As cockle 

 is usually not abundant, grows over a foot high, and is con- 

 spicuous because of its large pink blossoms, it can easily be 

 pulled from the growing wheat. The seeds have great vitality 

 and will germinate even if they have lain in the ground several 

 years. 



Wild Garlic (Allium vineale L.) is most troublesome to 

 wheat in eastern United States. It grows about two feet in 

 height. The flour is spoiled when the bulblets of the plant are 

 ground with the wheat. These can be removed by careful screen- 

 ing. Badly infested land should be put into cultivated crops 

 for a few years. 



Wheat-Thief (Lithospermum arvense L.). Other names by 

 which wheat-thief is known are bastard alkanet, corn gromwell, 

 redroot and pigeonweed. Its greatest damage is to meadows fol- 

 lowing wheat in rotation. Cultivated crops are the best remedy. 



Wild Mustard or Charlock (Brassica sinapistrum L.) is so 

 uniformly found in spring wheat that flouring mills make a by- 

 product of its seed. When not very abundant it is easily pulled 

 in the field, for it grows nearly as high as the grain and has con- 

 spicuous yellow flowers. In small wheat fields where it is very 

 abundant it can be killed by spraying the field with a 3 per cent 

 solution of copper sulphate, using about 50 gallons of solution 

 to the acre. It is claimed that the wheat is not injured. 1 If 

 wild mustard seed is covered with at least five inches of soil it 

 will not grow, but thus buried it will' retain good germinating 

 power for over 56 months. It comes up most abundantly 

 through one inch of soil. 



Thistles are of two varieties: Canada thistle (Cnicus 



arvensis), and common or sow thistle (C. lance olatus) . The 



latter is also known as spear, bur, and bull-thistle. It grows 



2 to 4 feet high and has the better hold on the land where both 



i Cornell Bui. 216 (1904), p. 107. 



