Pkthybridge and Lafferty — A Disease of Flax Seedlings. 377 



possible. Twenty seeds from a disease-free sample were placed on moist 

 filter paper in a Petri dish, and each seed was inoculated with a few conidia 

 from a pure culture of G. linicolum. Germination of the conidia took place, 

 and in some cases appressoria were developed. In a number of cases penetra- 

 tion of the germ-tubes into and development of mycelium within the epidermis 

 occurred. Twenty other seeds from the same sample, not inoculated with 

 conidia, but otherwise treated similarly, served as a control, and remained 

 free from mycelium. 



To prevent the seed from becoming infected would entail the prevention 

 of the spread of the fungus over the crop. Whether anything of value could 

 be accomplished in this direction by spraying during the growing season is a 

 problem which we have not yet approached, but is one which may be kept in 

 view for investigation when opportunity serves. 



Disinfection of infected seed would appear to be of more practical import- 

 ance under present circumstances, if it could be accomplished thoroughly 

 without difficulty and without injury to the seed. 



Before proceeding to any method of seed disinfection in practice, it would 

 be essential first of all to ascertain whether a sample of the seed proposed to 

 be sown contained any seeds infected with the disease. Diagnosis is not a 

 difficult matter, and it could be carried out at any Seed Testing Station 

 having a competent phytopathologist on the staff. The period required for 

 each test would not be longer than the ten days required for a germination 

 test of a sample of flax seed ; and the two tests could run concurrently. 

 Where, however, as at the Irish Seed Testing Station, the number of samples 

 of flax seed received for testing runs into some thousands in a season — and 

 that a short one — it would be a very considerable undertaking, requiring an 

 increased staff technically trained to cope with the work. 



Examination of seeds for pathological purposes is already carrried out at 

 the Irish Station in the case of some cereal diseases and also of celery seed ; 

 and as the number of plant diseases definitely proved to be transmitted by 

 seed is now a considerable one, this aspect of the work of a properly staffed 

 seed-testing station is likely to come into more prominence as time goes on. 

 There is no doubt that large, but certainly avoidable, losses are occasioned 

 annually in agricultural crops by the use for sowing of seed carrying disease 

 with it. 



Our first trials at seed disinfection with flax were started before it had 

 been clearly demonstrated that the source of infection lay in hibernating 

 mycelium contained within the epidermis of the seed-coat. They were based 

 rather upon the idea of killing any conidia which might be adhering to the 

 surface of the seed. In any case, however, disinfecting agents which killed 



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