234 FIELD CROPS 



plants are attacked at all stages of growth, from young seed- 

 lings to maturity. The best preventive measures are to sow 

 only clean seed from which all dirt and pieces of flax straw 

 have been removed, to treat the seed with the formaldehyde 

 solution (Section 195), and to grow flax on new land only, or 

 as a single crop in a rotation of several years' duration. 

 Much can also be accompUshed by saving seed from plants 

 which mature in flax-sick soil and hence are resistant to the 

 disease. Manure containing flax straw or from stock fed 

 on flax straw should not be put on land on which flax is to be 

 grown. Several other fungous diseases occur, mostly simi- 

 lar to flax wilt, though less serious, and yield to the same 

 treatment: Fortunately the crop is not very subject to 

 serious injury from insects. 



ROTATION, USES, IMPROVEMENT 



296. Place in the Rotation. On account of the fungous 

 diseases which attack flax when it is grown for seyeral years 

 on the same land, rotation of crops is particularly essential 

 if this crop is to become a permanent one in any locality. 

 On account of the common practice of growing it only on new 

 land, no definite rotations containing flax have yet been 

 established. To escape injury from flax diseases, this crop 

 should not be grown on the same field more frequently than 

 once in five years, and better results are obtained where 

 a cultivated crop and a grass crop are included in the rota- 

 tion than where small grains alone are grown. 



297. Uses of Flaxseed. Practically all the flaxseed pro- 

 duced in the United States is utilized in the manufacture 

 of linseed oil. There are two methods of extracting the oil. 

 from the seed, known as the old process and the new process. 

 The old process consists of crushing the seed, heating it to 

 about 165 degrees F., and placing it in sacks or between 

 cloths and forcing the oil out by pressure. The new process 

 differs from this in that the crushed and heated seed is placed 



