270 Scientific Proceedings^ Royal Dublin Society. 



Seed treated with 0-37 per cent., 0-48 per cent., and 0-59 per cent, 

 solutions respectively was sown in experimental plots, and untreated seed was 

 sown in a control plot alongside of them. The disease became evident in the 

 control plot and in the 0'37 per cent, plot as soon as the crop had brairded, 

 and these plots showed " stem-break " and " browning " well developed at the 

 time of pulling. The disease appeared much later in the plot sown with seed 

 treated with the 0'48 per cent, solution, and at pulling time " browning " 

 and " stem-break " were less evident in this plot than in the two just referred 

 to. 



The plants derived from seed treated with 59 per cent, solution showed 

 no signs of the disease, and they remained quite free from it through the 

 season. 



In the three cases where treated seed was sown, the crop was considerably 

 thinner than that derived from untreated seed, and thinner than might have 

 been expected, judging from the results of the germination tests of the treated 

 seed. It is clear that by spraying affected seed with a limited quantity of a 

 0'59 per cent, solution of formaldehyde the disease can be suppressed. But 

 the quantity of seed sown per unit area would have to be increased con- 

 siderably to ensure a crop of sufficient thickness, if this mode of control were 

 adopted ; and this might not be a profitable undertaking. 



Formaldehyde Gas. — Affected seeds were exposed to formaldehyde gas 

 when driven off by the action of potassium permanganate on a concentrated 

 solution, as well as when allowed to evaporate naturally from the solution 

 into a confined space of air. The results so far obtained, however, have not 

 been satisfactory, for, although the conidia are killed, the vitality of the seed 

 is much too seriously affected. Seed treated by the latter method was sown, 

 and the resulting plants arose and remained free from the disease, but they 

 were very few in number. It is hoped to carry out further trials with this 

 gas, paying special attention to time of exposure of the seed and temperature 

 of the gas. 



Heat. — A good deal of experimental work was done in connexion with the 

 effect of heat on flax seed. Thus, infected seeds were subjected to a tempera- 

 ture of 50°C. for periods varying from six to one hundred and ninety-two 

 hours. The effect on the fungus was nil, the conidia germinating just as 

 vigorously after heating as before, while the general effect on the seed was to 

 improve its percentage of germination. 



The conidia on affected seeds were also found to be unharmed by exposure 

 to a temperature of 70' C. for periods of from three to seventy-two hours. 

 Tests of the seed made just after treatment showed a considerable de- 

 pression in the percentage of germination, but after a period of rest, at room 



