An outline is given of an investigation that has dealt with disinfectant dusts containing mercury, and it is shown that the majority of the inorganic mercury salts are of little value in this respect. Some organic mercury salts have been tested and the result of laboratory and field work suggests that there is a close relationship between composition and fungicidal power. In the series R-Hg-X, where R is a hydrocarbon and X an acidic radicle, the fungicidal power appears to decrease with the increase of the molecule of R. A study is made of the significance of X in the methyl series and the results as they apply to disease control are recorded on a series of graphs.

The specificity of some of the compounds is noted and a brief mention is made of the treatment of seeds other than cereals.

It is suggested that there is no evidence for stimulation in the sense of tonic effect but that instances of better germination, growth and crop yields are due not only to the control of seed-borne organisms but to the preservation of the food reserves in the seed from the attack of soil organisms or mould organisms adherent to the seed.