6o6 



SCIENCE PROGRESS 



remains that flax crops cannot be successfully grown at as 

 frequent intervals as other crops. In the light of the experi- 

 mental work of Snyder, Wolff, Hodge, Tretiakov and others, 

 there can be no doubt that flax removes, if not less, at any rate 

 not more, nutritive materials from the soil than other farm crops. 

 In this connexion, the work of Prof. Snyder is of particular 

 interest and it is from his results that the following table has 

 been compiled for the purpose of showing the comparative draft 

 of various crops upon the soil : 



Among the points of interest which are brought out by this 

 table is the fact that a mangel crop is not a good crop to 

 precede flax because of the large withdrawal of nitrogen and 

 potash it occasions — substances upon which flax largely depends 

 for its rapid growth. It is evident also that a crop of flax is no 

 more exhausting to the soil than is an ordinary grain crop. 



Other evidence contrary to the view that flax is a particularly 

 exhausting crop has been furnished from the North Dakota 

 Experimental Station, where it has been demonstrated that 

 better crops of wheat l can be raised after flax than after wheat. 

 When writing upon this subject Prof. Boiling cites the confirma- 

 tory work carried out at Poltava by Prof. Tretiakov, showing 

 the draft on the soil to be less for flax than for wheat, even 

 when water evaporation is taken into consideration. 



Choice of Seed 



A number of forms of flax are cultivated at the present day 

 which exhibit differences sufficiently well marked for them 

 to be classified by some authorities into varieties of several 

 species. Flax, however, responds so markedly to a change 



1 It is not clear whether due allowance was made for the weeds which 

 presumably were left with the wheat crop and removed from the flax crop. 



