Lafferty — Disease of Cultivated Flax, 27 1 



temperature, this percentage regained its normal amount. Similar results 

 followed heating to 75° C. and 80° C. for periods up to 120 and 168 hours 

 respectively. 



Affected seeds were ultimately heated at 96'5°C. for periods varying from 

 three to thirty hours. The conidia survived a twenty-four-hour period of 

 treatment at this temperature in a viable condition, but not one of thirty 

 hours. Seed heated to this temperature for so long a period, however, was 

 fovmd to be permanently injured. It is true that the percentage of germina- 

 tion improved somewhat after a period of rest at room temperature, but it 

 never subsequently reached that of the unheated seed, the highest being 

 54 per cent., while that of the unheated seed was 94 per cent. 



Seed treated in this manner was sown in a plot, but, as was to be expected, 

 the resulting stand of plants was very thin. Moreover, they showed a lack 

 of vigour from the start, and they remained much stunted and dwarfed 

 promising a very poor yield of fibre. Nevertheless, the plants remained 

 entirely free from " browning " and " stem-break " throughout the season. 



From what has been said it may be inferred that the solution of the 

 problem of disinfecting infected flax seed without injuring the seed itself is 

 not an easy one.' Still, it is not to be regarded as hopeless, but rather as one 

 requiring more intensive investigation ; and further experimental work on the 

 matter is already in progress. 



No special study has yet been made regarding the question of the 

 possible existence of strains or varieties of flax resistant or immune to the 

 disease. But it lias been observed, contrary to what was thought in some 

 quarters, that both blue- and white-flowered varieties are liable to attack. 



VIII. — Summary. 



The present paper is concerned with a serious disease of flax which occurs 

 in the field in two forms, viz. — (1) " browning," a turning brown of the plants, 

 which occurs rapidly, especially under moist weather conditions, at or 

 before pulling time ; and (2) " stem-break," the fracture or partial fracture of 

 the stems of a certain proportion of affected plants, usually in the region of the 

 first node, and thus at or near soil-level. 



One and the same fungus was found constantly associated with the 

 disease in both of its forms. 



' In the trials made so far, death of the conidia present has been taken as the criterion 

 of disinfection of the seed. But it must be remembered that mycelium is also present 

 in the tissues of the seed-coat ; and this may possibly remain alive and capable of 

 developing new conidia when those already present are killed. 



