The present investigations have been carried out for the purpose of making clear the fungicidal actions of several fungicides, especially mercuric chloride ana Blasticidin-S to Piricularia oryzae CV..
When these fungicides were absorbed into the tissue of the rice plants through the roots, the degree of conidial germioation in dew drops formed on the seedlings was not always same as the number of spots formed by the blast fungous on the suscepts.
According to the Okamoto's proposal, inhibitory action of the fungicides through the suscepts on the conidial germination of the fungous or the growth of the mycelia belong to an indirect action of the fungicides. On the contrary, the writer has an opinion tha inhibitory action of the fungicides in dew drops formed on the seedlings of rice plants on the conidial germination of the fungous is not due to an indirect action of the fungicides but is due to a direct action, because in dew drops on the suscepts the conidia have been made contact with the fungicides and/or their compounds.
In the light of the present resuhs, the writer should like to insist thet inhibitory action to the fungous due to some physiological changes of the suscepts by the stimuli of fungicides must be called "Intensifying effect of fungicide against the disesse endurance of the suscept" (Intensifying effect).