Experiments with sterile cultures of peas, inoculated with their appropriate strain of nodule bacteria, have given the following results:

(1) In quartz sand the rate of excretion of nitrogenous compounds from the nodules was directly proportional to the capacity of the culture flask, i.e. to the supply of air to the roots.

(2) In water cultures abundant nodules were formed within the liquid medium. However, when all nodules were submerged, the plants grew poorly and their nitrogen content was low. The growth was the better, the more the nodules were situated above the liquid surface. The submerged nodules were, however, fully capable of fixing nitrogen, since the removal of part of the liquid with the subsequent exposure of the nodules to air resulted in a profuse growth of the plants. Nevertheless, in water cultures the excretion of nitrogenous compounds from the nodules was very slight or nil. The nodule formation was completely in hibited when all air in the medium was replaced by nitrogen gas.

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.

The efficiency of ten different strains of Rhizobium trifolii was studied with nitrogen free quartz sand cultures of red clover during three consecutive years.

(1) In the first season, distinct differences were noted in the size and nitrogen contents of the crops produced, after inoculation with ten various bacterial strains. These differences remained clearly discernible throughout the experimental period of 3 years: the individuality of the strains had not materially changed during this time.

(2) Reinoculation with the most efficient strain during the third year did not affect the plants.

(3) The loss of plants in winter was greatest in the jars which were inoculated with weak strains.

Spacing influences yield in that, beyond certain limits, the decrease in yield is proportionate to the increase in distance between the setts.

The limit to distance between the setts beyond which yield will fall varies with size of seed.

Seed size influences yield, large seed giving higher yields than small seed with the same spacing.

Size of seed influences the size of tubers produced. Small seed gives larger individual tubers than large seed with the same spacing.

Large seed possesses a greater number of sprouts per tuber than medium or small seed. Thus large seed gives rise to a greater number of true plants within the “hill”.

The greater the number of true plants in the “hill” the greater will be the number of tubers produced by the “hill” and the smaller will be their individual size.