8 SCIENCE BULLETIN, No. 9. 



condition of things is well known in Europe and America to flax-growers, and 

 it is the custom in Europe at all events to sow flax at intervals of not less- 

 than eight years on the same land, the flax being part of a rotation including 

 turnips, oats, clover, wheat, and beans. 



Bolley has found that this flax-sickness is due to the growth of a fungus 

 which he calls Fusarium lini, which lives in the humus of the soil and 

 attacks the flax-plant. 



Manuring of any description was quite ineffective in improving the growth 

 of flax or in destroying the fungus, nor did treatment of the soil with any of 

 the usual fungicides produce any better results. There appears to be no way 

 to rid the soil of the parasite, as the fungus lives in the soil for many years 

 without any flax crop to feed upon. This fungus does not appear to attack 

 any other crop. 



The remedies suggested are treatment of the seed with substances such as 

 formalin, and a five years' rotation of flax with wheat, hay, pasture, arid 

 maize. 



Bolley has also shown* that the deterioration of wheat-lands is brought 

 about by three or four parasitic fungi (in a later communication he gives the 

 number as at least five), whose growth is encouraged by the practice of 

 continuous cropping of the land with wheat, and which are propagated and 

 attack the wheat plant in exactly the same way as flax is attacked by 

 Fusarium lini. 



Similar instances of loss of crop-producing power have been long familiar,, 

 that of clover sickness being one of the earliest to be recognised. Peas, 

 beans, turnips, and cauliflowers are all subject to parasitic fungi which grow 

 on the buried portions of diseased plants and communicate the disease to- 

 healthy plants. The same is also true of many of the fungus diseases which 

 affect the potato, tomato, <fcc. 



Infertility often due to Bad Husbandry. 



In all these cases we have toxic conditions which are quite distinct from 

 the infertile condition brought about by soil-exhaustion, conditions which 

 are not dependent upon the richness or poverty of the soil, and which no 

 amount of manuring in the ordinary sense will remedy. Indeed, when we 

 consider the large stores of plant food in average and even in poor soils, the 

 comparatively small proportion removed by even the most exhausting crop,, 

 and the fact that this store of plant-food is being constantly rendered 

 available, it becomes difficult to realise that a few years' cropping can effect 

 such a complete removal of plant-food, as we must assume to take place if 

 the soil is exhausted in the manner usually recognised. 



As a matter of fact, analyses of European soils go to show that under 

 continuous cultivation there is little or no difference in the mineral content 

 of the soil. In short, the inferior crop-producing power of a soil after 

 repeated cropping is due to other and more obscure causes than the simple 

 depletion of the soil in plant-food. 



Press Bulletin No. 33, North Dakota Agric. Expt. Station, Oct. 1909. 



