1. With the aim of inducing reciprocal translocations of chromosomes in rice, soaked seeds of four varieties were x-rayed with the dose of about 20, 000 r. The plants from the treated seeds (X₁) and their progenies (X₂) were investigated. 2. The fertility of X₁ plants was remarkably reduced. 80% of main heads showed less than 50% fertility and those with the fcrtility under 20% were the commonest. No difference was found among the varieties in the degree and the mode of sterility. The reduction was aiso found in the number of tillers. 3. The sterility of tillers from iower nodes somewhat differed from that of main culm in X₁ generatiori. The secondary tillers had generally the same degree of sterility with primary ones from which they grow.

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The resistance to rice blast disease is one of the important characters treatedin the breeding of rice plants and the selection for the chara cter is usually made in F₃ or F₄ generation of hybrid. An attempt to practise an individual selections in the F generation for the resist ance of the disease was undertaken in this exp eriment. The resistant lines were obtained with more accuracy in the F₂ individual selections.but the selections of other economic characters were not so effective. So it is considered as the result tha.t the F₂ individual selection is a better method when the resistance to rice blast is the main purpose of breeding.

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In the present paper dealt with the gical comparison of the dipioid and tetraploid sugar bee.t on the early stage characters shown by water culture. l) The getmir, ation of tetraploid seeds was noticeably poot as compared withthat of the dipioid. 2) The growth of leaves and roots of the dip ioid seedling was more vigorous than those of the tetraploid. 3) The diploid plant surpasses the tetraploid in the yields of tops and roots as well as the number of leaves. 4) The stomata of the tetraploid are larger in size and smaller innumber compared with those of the diploid. 5) The osmotic pressure in the diploid plants was proved to be higher than that in the tetraploid ones. 6) The carbon assimilation was Inore vigorously going on in the diploid than in the tetrapioid.

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l. This work is one of the stucdies in whichthe writers intend to make cle.ar the modes of quantitative inheritance in main crops from the view point of breeding. Materials used are the same as those used for the study on the inheritance of panicle already des cribed in the previous reports (SYAKUDO, et al. 1952.), namely the F₁-F₅ generations from the hybrids of "NABESIMA" and"KAIRYO-AIKOKUHEN-DAIKOKUGATA", whlch were crossed m 1945 at tne plant-breeding laboratory of the KYOTO Univ. The total numbers of lines and ir!-dividuals observed are l, 137 and 85, 616 respectively. 2. "NABESIMA" is a normal variety Showing a medium length of panicles and also a medium c_ulm height (about 90 cm.), while 'KAIRYO AIKOKUHEN-DAIKOKUGATA" is a dwarf variety with short panicles and short culm height (about 70 cm.). 3. The methods of investigation are the same as those already described in the previous report (SYAKLTDO, 1948-C). 4. The progeny test in regard to the culm height was made considering the mean value, standard deviation, coefiicient of variabilitvy and the range of variance.The results show that the two multiple genes H₂ and H₃ and a dwarf gene D₁ determine the culm height.The accumulative effect of the gene P₄ and P₅ (SYAKLTDO et al. 1952) to the culm height are of imperfect dominance, while that of D₁ is of perfect dominance. The genotypes of the parents wiil be assumed as follows:-

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1. In the present investigation were studied the fertiiity and germination of the seeds of F₁ plants, and the external characters, fertility, and somatic chromosomes of F₂ plants of backcrossed hybrids raised from Triticum-Secale triple F₁ hybrids pollinated with the pollen of Triticum turgiaum. 2. The number of somati_c chro, mosomes of the backcrossed F₁ plants that had shown the fertility was 30, 31 and 32. The fertility for spikelet in these backcrossed F1 plants having 2n= 30 chromosomes appears to vary from 5.0 to 11.3 percent, that to the case of 2n=31 chrom, osomes to vary from 1.3 to 31.4 percent and that in the case of 2n=32 chromosomes has shown 5.8 percent respectively (Table l). 3. The percentage of germination of F₂ seeds obtained on the backcrossed F₁ plants having .2n=30 chromosomes appears to vary from 5.6 to 43.8 percent, that in the case of 2n=31 chromosomes has shown to be 6.7 percent and that in the case of 2n=32 chromosomes 20.0 percent, viz. the seeds from F₁ having 2n=30 chromosomes showed the highest percentage in germination.

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The pollen development and fertility in Agmpanthus umbellalus L'Her have been studied and the following results were obtained. 1 Agapanthus umbellatus L'Her was the diploid plant and no abnormality o melosls in pollen mother cells were observed. 2. The percentage of pollen germination was 12.5-32.7%. This number m.ay be seen too small because the observation was made only one hour after pollination, and so the real number of pollen capable of germination would be higher . 3. Two methods of pollination were used, one was cross-pollination and the other was openpollination. The results were somewhat better in the case of open-polliatio-n, namely 258 flowers were pollinated and 33 capsules were fructified, the percentage of fructified capsules for pollinated flowers were 12.8%. In the case of cross-pollination 31 flowers were pollinated but no copsule was fructified. 4, . The seed of Agapanthus umbellatus L'Her has a fcather on one side and shape of capsule is fong ellipse with high three mounds. 5. Three kind, s of seed were recognized in the capsule; D. erfect seeds, imperfect seeds, ' and sterile seeds. In the 2nd type, the seed development was not perfect, and the 3rd type was considerd that the growth of ovule was not, complete. Th:e percentage of the perfect seeds above men.tiori, ed was only 3.8-29.2%6. The cause of high sterility in Agapalethus umbellatus L'Her could not be recognized cytological relation but seemed to be 'high relation with the, equilibrium of nutriment between sexual organ and nutritive organ. The remarkable vegetative development of nutritive organ was considered to has important correlation with. the fruit-bearing.

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In higher plants, the fertilization is fcllowed by the development of embryo and endosperm. Recently, many papers have reported that the development of embryo is influenced by the substances in endosperm. The isolated embryos of Cucurbita moschaia as young as 25-30 days after poliln., tlon were germinated and well grown ile viiro under aseptic condition on an agar medium, which contains 2% sucrose and mineral salts (pH 5.6). But on a medium added water extract of Cucurbita endosperms which was collected from seeds as young as 10-20 days after pollination, the roots of young seedling was inhibited to develop., the cortex in the root was broken down, and epidermis was spilited open (T-able 1, Fig. 2 and3). Effects of pH and osmotic pressure of medium to root development were examined (Table 2 and 3), and the fact was found that the phenomena above-mentioned was r.ot occured by change of pH values and osmotic pressure of medium. Therefore, it seems that a root inhibitingsubstance is present in the endospem of Cucurbita seeds. The root growthwas inhibited on an agar medium contained heteroauxin (Tabl 4), but the phenomena in this case differed from that on the medium contained endosperm extracts. So that, it seems that the root-inhibitor is notthe same to auxin itself. The root-inhibitor was also proved as heat stable. It is s, u:pposed by the auther that the root-in-hibitor is connect-*d with the development of embryo (Fig 1.).

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1) Comparative study between diploid and tetraploid buckwheats, Fhagopyrum esculepttuam, have been made concerning the contents of water and total nittogen in several organs at different stages of growth. 2) On the whole no significant difference was :noted between the diploids and the tetraploids in the relat.ive, total amount of water and of total nitrogen during their whole growth period. It was, however, noticed that the mode of change in the contents of these substances was remarkably different between the two in some organs as well as at some stages of growth. 3) Significant difference in- water content was displayed in the stem at two stages, vis., the beginning flowering and the early fruit develop ment, giving higher content in the diploids than in the tetraploids. Although not significant, the leaves of the tetraploids were observed always to shotv the tendency of having higher water content than those of the diploids throughput the period from germination to early fruit development. At the stage of maturity, however, the situation was quite reversed, the latter being predominant in the content than the former.

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The percentages of germination of F₁ seeds, dyad cells, good pollen grains and the fcrtility of F₁ piants obtained by crossing between 8 varieties of Abel. esculerdu's and I variety of Abel. Manihot wcre different with the varieties of the mother plant, ranging ca.2.7%-83.3%, ca. 83.7 %-99.3%, ca. 28.9%-90.8% and ca. 0.00-0.22 per pod respectively. The F₁ strains showing the good percentage in the gerrnination of F₁ seeds were also superior in the other characters, while those tnat werepoor in the germination were also inferior in the other characters.

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