DISEASES OF CULTIVATED PLANTS 611 



if they are made thoroughly wet, or if they are allowed to stay quite 

 damp for some hours. The grain must be handled over immedi- 

 ately after treatment until it is found to be dry. Note: The seed 

 should be thoroughly cleaned by running through a fanning mill 

 before it is treated because the solution is not strong enough to kill 

 the disease (fungus) which is inside of bits of straw and chaff. 



Summary With Notes. 1. There is a diseased condition of 

 flax soils which has long been known to farmers in flax producing 

 regions as flax sick soil. 



2. If flax is sowed rather continuously for a number of years 

 upon the same soil this disease tends to thoroughly infect the soil 

 so that flax growing becomes no longer profitable. 



3. The disease may be spread by way of the seed flax. 



4. The plants attacked die at all ages as if attacked by wilt; 

 hence I have called the disease the flax wilt disease. 



5. The direct cause is a minute fungus parasite which grows 

 on the inside of the flax plant, starting either from the seed, or by 

 attacking the roots of older plants if the soil has previously been 

 infested. 



6. There are many ways in which the infection might reach 

 new fields, but the chief one is by way of the seed. 



7. The seed (spores) of the parasite gets into the seed flax 

 at threshing time, rattling off from the sides of the flax straws which 

 have been attacked by the parasite. 



8. When such infected flax seed is sown, the spores of the 

 fungus germinate and at once attack the young plants. Those 

 attacked early die at once and there may be no stand even from 

 good seed if the spores of the parasite are abundant. When once 

 in the ground the fungus spreads rapidly, attacking new plants 

 throughout the season. It can live from year to year upon the 

 humus of the soil, hence the soil is soon ruined for flax. Six years 

 of continuous seeding of flax upon the same plot at the Agricultural 

 College thoroughly filled the soil with the parasite and no plants of 

 flax can live there longer than three weeks. 



9. All other farm crops do well upon the flax sick soil. Tt 

 has not lost fertility for flax, as is proved by experiments which 

 destroy the spores without injuring the soil. 



10. The fungus belongs to a genus of plants which botanists 

 have called Fusarium. As this is a new species, we shall call it 

 Fusarium lini. 



11. Much of the soil of this state has not yet been infected; 

 but about 50 per cent, of all samples of seed flax yet examined 

 show the presence of the Fusarium spores. It is probable that no 

 sample of flax seed is entirely free from infection. 



12. When the soil is once infected no way is known to rid it 

 of the parasite. The fungus is able to live in the soil for many 

 years without the presence of a flax crop to feed upon. 



13. The seed flax should be thoroughly graded and cleaned 

 in a fanning mill before treating. This will remove all of the bits 



