378 Scientific Proceedings, Royal Dublin Society. 



the conidia might also be expected to kill the resting mycelium, although, 

 perhaps, not quite so readily or completely. 



Two experiments were first carried out with seed which had previously 

 been proved to be free from the disease. Some of the seed was artificially 

 contaminated with conidia of Colletotrichum derived from a pure culture, 

 while some of it was not thus contaminated and served as a control. The 

 contaminated seed after drying was disinfected either by spraying with dilute 

 solutions of formaldehyde, or by steeping it for short periods in such 

 solutions ; and, after drying, it was sown. 



It is not necessary to record here the full details of these experiments, 

 but the results may be summarized briefly. The uncontaminated (control) 

 seeds produced healthy seedlings only in all cases. The contaminated but 

 not disinfected seeds in one case produced eighty per cent., and in the other 

 forty per cent, of diseased seedlings. Spraying the contaminated seeds before 

 sowing with dilute formaldehyde solution by means of an atomiser reduced 

 the incidence of disease from eighty per cent, to fifteen per cent. Steeping 

 contaminated seed in dilute formaldehyde solution completely suppressed 

 the disease in seven trials, and, in the only other one made, reduced it from 

 eighty per cent, to two per cent. Where the seed was steeped in weak 

 solutions for short periods (two to three minutes) there was no adverse effect 

 ou the germination of the seed or the development of the seedlings ; but 

 where the steeping was prolonged (six to ten minutes) the effect was to 

 reduce the germination very markedly (in one case from 97 per cent, to 

 59 per cent.) ; and the seedlings which appeared were in many cases seriously 

 injured by the treatment. It was clear that soaking flax seed for several 

 minutes even in weak formaldehyde solutions would not be a practicable 

 method of disinfection of the seed owing to the bad effects mentioned. 

 The best results were obtained when the time of steeping was two minutes 

 and the strength of solution 1 : 400 or 1 : 300 of forty per cent, formalin 

 in water. 



The- next trial was made with naturally infected seed. This, when sown 

 untreated, produced twenty-four diseased and seventy healthy seedlings. 

 When steeped before sowing for two minutes in formalin, 1 : 400 and 1 : 300, 

 the disinfected seed gave rise to ninety-three and ninety-four seedlings respec- 

 tively, amongst which there was only one diseased seedling in each case. In 

 this trial, therefore, the germination of the seed was not interfered with at 

 all, and the disease was reduced to a minimum, althougii not completely 

 eliminated. 



This result, although extremely gratifying, cannot be regarded as entirely 

 satisfactory, for, if even a comparatively small number of infected seedlings 



