Under anaerobic condition, Piricularia oryzae ceases its growth. The optimum temperature for the growth of the fungus is about 28°C. Nitrate is not reduced though it is available to the fungus. Nitrite seems to be injurious to the fungus.
As to the carbon sources, glucose is effective but starch is not so much useful. Cellulose and pectic matter are also useful, but the latter seems to be still more available.
Oxydase and dehydrase are proved in the culture of the fungus.

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According to the inoculation experiment with Piricularia oryzae to the young blade of adult-tillering-rice, the fungus forms at first the brown coloured appressorium on the host, and then enters the epidermal cell piercing through the outer layer of the epidermal membrane, if the latter is not so highly silicified as that of the dumb bell shaped rice-cell, the various trichomes and the papillalike bodies of the outermost layer of epidermis.
The motor-cell and the accessory cell of the stoma seem to be the portions most easily infected.
In the case of the inoculation to the base of the ear-Hokubi-when it is just the time of earing, the fungus enters the host cell as in the case of the blade but with difficulty. Among the epidermal cells of the inoculated portion, the long cells situated on the upper parts of the assimilating parenchyma near the nodes of the racheae and the cells of the bracts projected from the basal nodes of the ears are observed to be the portions rather easily infected.
The penetration begins with the emergence of the slender penetration hypha at the central part of the under surface of the appressorium. Then the infection hypha pierces the outer layer of the epidermal membrane and enters the cavity of the affected cell. When the hypha reaches the inner surface of the membrane, soon forms a small vesicle. Sometimes the callosity may be observed at the inner surface of the pierced membrane. After this, vegetative hyphae may be formed branching from the vesicle or by the conversion of the latter.
The morphological and anatomical structure of rice, especially of its epidermis has been described.

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1. This paper deals with the effects of the hydrogen ion concentration of the media of the bacteria (Bacillus A, B and C isolated from the interior of rice seeds) on their thermal death times.
2. The experiments were carried out by such method that the test tubes containing 10 cc of the bouillon nutrient broth, the reaction of which had been adjusted to pH 5.0, 7.0 or 7.2, and 8.6 or 8.8 (after steam sterilization) with N/1 HCl or NaOH, and in which the bacteria were suspended, were placed for various lengths of time in a water bath, the temperature of which was electrically controlled, after which the tubes allowed to stand for two or three days at 28°C. The bacteria tested were cultured in bouillon with reactions of pH 7.0 or 7.2 for 24 hours at 28°C. Nine strains of Bacillus A, four strains of Bacillus B, and two strains of Bacillus C were used.
3. The thermal death time of Bacillus A at 47.5±0.5°C. seems to fall between 35 and 60 minutes in the medium of pH 5.0, between 15 and 50 minutes in that of pH 8.6 or 8.8, and in more than 60 minutes in that of pH 7.0 or 7.2; that of Bacillus B at the same temperature in more than 60 minutes in that of pH 5.0 and 7.0 or 7.2, and between 25 and 35 minutes in that of pH 8.6 or 8.8; while that of Bacillus C at the same temperature seems to be more than 60 minutes, regardless of the hydrogen ion concentration of the medium.
4. The thermal death time of Bacillus A at 50±0.5°C seems to fall between 10 and 20 minutes in the medium of pH 5.0, between 15 and 60 minutes in that of pH 7.0 or 7.2, and in less than 5 minutes or between 5 and 10 minutes in that of pH 8.6 or 8.8; that of Bacillus B at the same temperature between 10 and 20 minutes in that of pH 5.0, between 20 and 25 minutes in that of pH 7.0 or 7.2, and in less than 5 minutes in that of pH 8.6 or 8.8; that of Bacillus C at the same temperature between 50 and 60 minutes in that of pH 5.0, in more than 60 minutes in that of pH 7.0 or 7.2, and between 15 and 30 minutes in that of pH 8.6 or 8.8.
5. The thermal death time of Bacillus A at 52.5±0.5°C seems to fall between 5 and 15 minutes in the medium of pH 5.0, between 10 and 20 minutes in that of pH 7.0 or 7.2, and in less than 5 minutes or between 5 and 10 minutes in that of pH 8 6 or 8.8; that of Bacillus B at the same temperature between 5 and 10 minutes in that of pH 5.0, between 15 and 20 minutes in that of pH 7.0 or 7.2, and in less than 5 minutes in that of pH 8.6 or 8.8; that of Bacillus C at the same temperature between 10 and 20 minutes in that of pH 5.0, between 20 and 25 minutes in that of pH 7.0 or 7.2, and between 5 and 15 minutes in that of pH 8.6 or 8.8.
6. The thermal death times of Bacillus A and B at 55±0.5°C. seem to fall in less than 5 minutes, irrespective of the hydrogen ion concentration of the medium, excepting that strain No.22 of Bacillus A, isolated from the seed of Ogami, a variety of rice, were killed in less than 10 minutes in the medium of pH 7.0 or 7.2; that of Bacillus C at the same temperature in less than 5 minutes or between 5 and 10 minutes in that of pH 5.0, between 10 and 15 minutes in that of pH 7.0 or 7.2, and in less than 5 minutes in that of pH 8.6 or 8.8.
7. Regardless of the hydrogen ion concentration of the medium and of the strains tested, the thermal death times of Bacillus A, B, and C seem to fall in more than 60 minutes at 45±0.5°C and in less than 5 minutes at 57.5±0.5°C. and 60±0.5°C.

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