(1) In 1957-1959 357 varieties belonging to O. sativa which were collected from various districts of the world, 50 varieties belonging to O. glaberrima and 38 samples belonging to 12 species of wild rice were tested on the leaf-blast resistance by spraying or injecting at the seedling stage spore-suspension of 3 or 4 races of the fungus. (2) As shown in tables 3-6 the tested varieties reacted differently to 3 or 4 races of the fungus. Namely, the majority of Indica type varieties belonging to O. sativa which were introduced from the countries of southeastern Asia and most of the varieties belonging to O. glaberrima showed high resistanc.e to all of the 3 races, while most of Japanese varieties and Japonica type varieties introduced from Taiwan, U. S. A., Philippines and Egypt were susceptible to all of them. (3) A conspicuous difference in the blast resistance was recognized among the samles belonging to each species of wild rice. This indicates that there is no any specific relation betweeh the genome constitution and the blast resistance of wild rice. (4) The facts mentioned above indicate that for breeding highly blast resistant varieties of rice it is of the most importance that the blast resistance genes are introduced from the varieties which are highly resistant to many races of the fungus.

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The important characteristics of economic plants and animals from the view-point of breeding are usually expressed as continuous random variables which are analyzed statistically to see the genetical behavior of those characteristics. In the case, the linear models are postulated for the genetical structure of the characteristics. Accordingly many genetical parameters such as genetic variance, environmental variance, heritability, genetic correlation etc. are defined. To extend breeding techniques it is desirable to use such parameters if they exist. But the estimators of these Parameters always vary according to the sampling and the parameters themselves change under varying situations. Then we adopted the heritability, one of genetic parameters, as a clue of the study for the purpose to see whether the analysis of quantitative characteristics by means of such a method with genetic statistics is useful or not for the actual breeding, because the heritability is meaningful, historically and somewhat practically, to combine genetic statistics with actual breeding. Experiments were conducted on paddy rice plants, for two years at four localities, soybean plants for five years at four localities and silkworms for two years at three localities. The estimators of heritability were calculated by various methods and in. vestigated based on the data of these experiments. In this first report, details of our purpose and opinions for the experiments are described. Concerning with them, adopted methods estimating the heritability and the confidence intervals of these estimators(as possble to set up)are also introduced.

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For study of somatic mutations two clones of Cosmos bipinnatus were used. One was heterozygous both fcr flower color and flower-type, whiie the other was heterozygous for flower color only. Induction of somatic mutations was easily detected by the appearance of streaks with sharp outlines of different colors on a background of normal color of the ray florets. Plants of both the clones were irradiated at different stages of flower development, which was controlled by giving short day treatments for various periods of time following continuous long day treatment. The average height of plants decreased as a result of irradiation. The decrease in plant height increased with the increase in dose of irradiation. Narrow streaks to wide sectors of red, Iight pink, and' white colors were observed on a background of normal color of Clone I and mutant sectors of light pink and white colors were observed on a background of normal red color of Clone II. Mutation rate was calculated on the basis of percentage of flowers with mutations. It increased with the dose up to an optimum dose, after which a decrease in mutation rate was observed with the increase in dose. Highest mutation rate was observed after 30 days, in Clone I and after, 10 days short day treatment in Clone II at 2 Kr. Some difference in the two clones was noted as regards the stage at which niaximum :mutations were induced. The number of flowers having mutant sectors bigger than half the width of the ray floret was generally larger at the vegetative and younger stages of flower development than at the advanced stages. The number of mutations increased up to a few weeks after initiation of flowering, but later on it gradually decreased. Greater decrease in number of flowers with mutations was observed as more time elapsed between irradiation and flowering. But the proportion of flowers with bigger mutant sectors increased after greater lapse of time between irradiation and flowering. Flowers with physiological injuries and morphological abnormalities were observed on irradiated plants of both the clones.

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(1) The author bred up a new amphidiploid plants at the progeny of the cross between “ Fuyo ” (H. mutabilis) (2n = 92) and “ Kusa-Fuyo ” (H. Moscheutos) (2n = 38). (2) The main characters of these new amphidiploid plants were as follows : These amphidiploid plants showed heterosis. The characteristics of stem and leaf resembled H. mutabilis which are shrublike. The flower size was larger, the flower coloring more beautiful, the beginning of flower openning earlier and the flower period was longer than the parents. Moreover the pollon fertility was as high and the size of pollen grains was larger than the parents. The seed shape was similar to H. mutabilis. The seeds had many surface hairs like H. mutabilis, but their color was darker than H. mutabilis, and their size was larger than in length, width and thickness. (3) In these amphidiploid plants, the chromosome conjugation at MI of PMCs showed 65_II with no irregularities. The chromosome number in root tips was 2n=130. (4) The author wou.Id like to propose that these new amphidiploid plants be given the Japanese name “ Ai-Fuyo ” and the scientific name H. muta-moscheutos KUWADA.

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Abnormal segregation for waxy and apiculus coloration, which is explained by assuming the presence of a gametophyte gene, ga linked with wx and C, was described. The irregularity of waxy segregation in these studies was first observed in the F₂ of a cross between a non-waxy progeny (wx+wx+1g+1g+C+C+) from plants exposed to the atomic bomb in Nagasaki, and a linkage tester characterized by waxy, Iiguleless and apiculus coloration (wx wxlg lg C C) (Table 1).

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Comparative studies on the morphological development of rays in the various flower-types were reported in a previous paper (SAMATA, 1962). Emphasis in the present paper is placed upon the comparison of disk development with special reference to the action of genes on the expression of disks. Materials used in this experiment were the single type, doubled types of different degrees of specialization and the pompon-doubled type.

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Effects of 2, 4-dinitrophenol (DNP) solution on the frequency of chromosome aberrations induced by X-rays were investigated in the present experiment, using germinating seeds of a two-rowed barley. The seeds pre-soaked for 24 hours were irradiated with 150-300r and were treated with DNP solution (10^-4M) at various times after or before irradiation. Cytological observations were performed on root-tip cells, fixed at 49.5 hours after soaking when many cells were in the anaphase of the first mitotic division.

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