Pethybridge and Lafferty — A Disease of Flux Seedlings. 381 



Finally, the idea of first very slightly moistening the seed with a misty 

 spray of water and then drying it off at once by mixing a dry fungicidal 

 powder with the seed was acted upon. 



The powders used were— (1) the dried precipitate produced when a solu- 

 tion of copper sulphate is acted on by milk of lime, and (2) a finely ground 

 mixture of copper sulphate crystals and dry sodium carbonate. Both of these 

 powders are sold commercially for preparing potato-spraying mixtures.although 

 such preparations have been proved to be less efficacious in warding off the 

 potato blight than freshly prepared Bordeaux and Burgundy mixtures. 



The results of the treatment were very encouraging. With the dried 

 precipitate mentioned, the percentage of diseased seedlings arising from the 

 treated seed was only two, whereas in the case of the same seed untreated it 

 was thirty-five. Treatment with the mixture of copper sulphate and sodium 

 carbonate gave even better results, for in this case not a single diseased 

 seedling appeared during the experiment, which lasted for three weeks, a 

 period which experience has shown is much more than ample for the appear- 

 ance of primary infection. 1 



It is perhaps needless to say that all the attempts at seed disinfection 

 dealt with in the present paper were carried out on a small scale ; and it is 

 not claimed that any one of them would necessarily be practicable under 

 field conditions. Nevertheless we consider that sufficient has been done to 

 show that, working along the lines indicated, there is a good prospect that 

 further trials, on a more extended scale, would result in the working out of 

 a method of treating flax-seed infected with the Colletotrichum disease, 

 which could be used in actual practice, and which would, if persevered with, 

 ultimately lead to the disappearance of this malady from our flax fields. 



IX. — Distribution of the Disease. 



It has already been pointed out that a Colletotrichum disease of flax 

 occurs in the United States of America. It appears to be especially prevalent 

 in the State of North Dakota, where Bolley studied it. It is, however, 

 not certain that Bolley's disease is identical with that described in the 

 present communication, for we have been unable to discover any signs of 

 internal attack upon the embryo while within the seed, as Bolley did. 



1 While the present paper was passing through the press the results of further seed- 

 disinfection trials became available. Sulphur was found to be quite useless as a disin- 

 fecting agent for this disease. Dry infected seed exposed for two hours to moist 

 formaldehyde gas was almost, but not quite completely, disinfected ; and no adverse 

 effect on the germination of the seed or the development of the seedlings was observable. 

 Exposure for four and six hours was scarcely more effective in killing the hibernating 

 mycelium, and caused severe injury to the seed. 



