( 1 ) Studies were made on the interspecific hybrids between Hibiscus coccinea and H. moschata which were different in their origin from the materials used in the previous experiment. The materials used in the present study are now maintained at both Kyoto and Kagawa University, but how the parent plants and the F₁ Plants were obtained is not clearly known. ( 2 ) The F₁ plants showed heterosis. The F₁ plants started to flower earlier and continued to iflower longer than the parents, so that the duration of flowering period of the former was extremely long. The flowers of the F1 were larger in size and prettier n color than those of the parents. ( 3 ) The conjugation of the chromosomes in PMCS of the F₁ plant was quite as good as in its parents, and more than 90 per cent of the PMCs could form spore quartets. The pollen and seed fertilities of the F₁ were both very good. The number of seeds per pod of the F₁ was intermediate of the both parents. The chromosome numbers in the root tip cells of the parents and the F₁ were all 38. ( 4 ) The size of F₂ seeds was quite similar with H. coccinea, and their germination rate was 50-60 % which was as good as in the parents. The growth of the F₂ plants showed intermediate of both parents or resembled either one of the parents, showing no such heterosis as in F₁

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Accoring to the criterion of developmental stages established in the preceding paper (FUKUl, J, and GOTOH, T., in press), the authors intended to make clear the effect of day-length and temperature upon the development of floral organs and its varietal differences. Sango-wase-daizu (early variety, Ia), Norin No. 2 (rriiddle variety, Ilb) and lpponsuzunari (1ate variety, Vc) were cultivated in fcur plots, that iscontrol plot (natural day-1ength, in outdoors), shortday plot (10-hours day-length in outdoors), high temperature plot (natural day-length, in greenhouse which is 3-4°C higher than outdoors) and short day high temperature plot (lO-hours day-length, in greenhouse). Ia, Ilb and, Vc are symbols of ecolo gical types as deflned by FUKUl, J. and ARAI, M. (1951). In control plot, Sango-wase-daizu bore flower primordium 10 days after cotyledon unfolding and floral organs developed rapidly. Norin No. 2 and lppon suzunari bore flower primordium 24 days after cotyledon unfolding. The development of floral organs was faster in Norin No. 2 than in lpponsuzunari.The development of floral organs of lpponsuzunari was very slow, especially inl early stages (from stage1 to stage ll). The day-length was capable to in duce the flower primordium formation but it was too long for the normal development of floral organs. As plant age proceeded, plants became more sensitive to day-length, so fioral organs developed slowly to stage 11. After stage 12, floral organs developed at the normal rate and soon flowering occurred, since the process after stage 12 was in.sensitive to day-length. By short-day treatment, both flower primordium formation and development of floral organs were accelerated in the all varieties, the degree of acceIeration being larger in late variety, rather little, in middle variety and little in early variety. In the developmental course of floral organs, the early stages, that is, from stage 1 to stage 11 hours) day-length, the flower primordiuirl formation was accelerated in Sango-wase-daizu and Norin No. 2 the critical day-lengths of which were longer than 14.5-15 hours. In lpponsuzunari the critical day-elngth of which was near 14.5-15 hours, the flower primordium formation was rather reta.rded. The developmen.t of floral organs was accelerated in the all three varieties. By the elevation of temperature under 10 hours day-1ength, the flower primordium formation was accelerated in Sango-wase-daizu and lpponSuzunari, but not in Norin No. 2. The development of floral organs was accelerated in all the three varieties. The acceleration of development of floral organs by the elevation of temperature was general but an especially sensitive stage ivas not obvious.

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l. Strains were developed, which involved rather wide range of sterility, from an original cross between Tadukan, donor Philippine variety, and Norin 8, recurrent Japanese variety, by backcrosses repeated 3 times, in which hybrid plants were aiways used as fcmale and the recurrent variety as male parent. Several strains, referred to as Tastrains in the following, were finally obtained by selection on fertility from the subsequent pedigree generation ; however, they had a slightly lower fertility than the average Japanese varieties, although their pollen and embryo sacs were function-ally normal. 2. The F₁ hybrids of these Ta-strains with Japanese varieties revealed a contrasted difference in fcrtility in reciprocal crosses : F₁ hybrids with Japanese varieties used as the male parents revealed a wide range of sterility, while all F₁ hybrids from the reciprocal crosses were normal in fcrtility. These results indicate that the sterility might be due to an interaction between the cytoplasm and nuclear genes. 3. The degree of the sterility of the F₁ hybrids from Ta-strains × Japanese varieties seemed to indicate two groups involved in Japanese varieties, i.e. the one giving rather low sterility, and the other the higher sterility in F₁ hybrids. 4. The sterility above stated was considered ta be intimately connected with the difficulty in anther dehiscence, the sterility range showing a close correlation with pollen dispersal. 5. The cytoplasm connected with this particular sterility in these Ta-strains was considered to have originated from the one in Tadukan, retaining the reaction norm over many backcross generations by the Japanese varieties.

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The purpose of this series of study was to get some informations about the physiological process of floral differentiation. In the previous paper the author reported on the distribution of polysaccharides and their changes in quantity in shoot apex during the organogenesis of foliar and floral primordia. In this paper, the distributions of RNA and of protein in shoot apex were investigated histochemically, and the changes in quantity of amir.O acids and soluble sugar (glucose, fructose and sucrose) were determined by means of paper chromatography. The localization of protein in shoot apex and floral bud was almost coincided with that of RNA, and most of those substances were distributed mainly in the regions where polysaccharides were not deposited or a little. In other words, the concentrations of RNA and of protein were high in foliar and floral primordia where the active growth and d.ifferentiation were occurring. The changes in quantity of soluble sugar in shoot apex during the floral differentiation were closely connected with the changes of concentration in polysaccharides reported in the previous paper. The changes of amino acids were also related to those of RNA and protein. According to the facts obtained in this study it may be suggested that the flower bud differentiation and its growth in rice plant proceed from the physiological processes in shoot apex. Namely, the increase in polysaccharides accumulation in the tissue that has meristematic potentiality induces the reduction of their synthetic action, and this causes the tonversion from the active state of polysaccharides synthesis into the state of active protein synthesis and polysaccharides decomposition The same relation was also observed in the stage of vegetative growth and the early stage of generative growth when the shoot apex has already transformed into a young ear.

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Dry seeds from a foundation stock of a rice variety Norin No.29, were treated with two doses of gamma rays from ⁶⁰Co, that is 10, 000 r and 30, 000 r The frequencies of chlorophyll mutations in the X₂ progenies from ears having 25 or more seeds were greater with 30. 000 r irradiation than with 10.000 r (Table 2) . Using these materials, mutations which affect quantitatively inherited characters were studied. The polygenic traits chosen were grain-size characters, such as length and width of grain, because it is technically simple and more than one measurement of the character can be made on each individual. With such spatially repeated characters the phenotypic variance can be partitioned into variance within individual and variance between individuals (Table 1). In each X₂ or X₃ plant five seeds were measured with respect to their length and width. As shown in Tables 3 and 5, the means of all treatments agreed well with each other on both length and width. However, effects of irradiation were remarkable for increased variances between individuals. An increment in variance per unit dose was tabulated in Table 7. The relatively smaller variance increment per unit dose in population treated with 30, 000 r might have resulted from the frequent occurrence of deleterious mutations and/or chromosomal aberrations caused by the high dose of irradiation. The lower rate of induced genetic variation in X₃ population, compared with that in X₂ populations, seemed to be ascribable to an increase in the frequency of genetic deaths due to the ho-mozygosity of harmful genes in the X₃ generation. The calculated coefficients of correlation between length and width of grain in the X₂ generation were shown in Table 4. It is very interesting to note that the correlation coefficient for 30, 000 r irradiatin was of the same magnitude as was obtained in the control population. This was ascribed to the lowered viability of plants having a short and broad grain-shape, as was readily seen in Figure 2. Effect of gamma irradiation for that correlation was remarkable in the X₃ generation, that is, the correlation coeficient was 0.4000, -0.0020 and 0.1615, respectively for Or, 10, 000 r and 30, 000 r irradiated populations (Table 6 and Figure 4). These results suggest that both grain-size characters are controlled by different neutral genes and the cause of variance increase must be due to the mutations induced in polygenic systems. In order to obtain a maximum amount of genetic variance in quantitative characters, we must irradiate the material with lower doses than when inducing mutations in major genic systems.

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The authors determined 3 main genetic factors affecting the growth habit of wheat in report 1. Among these 3 factors, E factor determines erect type, and both P and T factors control prostrate type though they differ in their effects on prostrate t ype. We also clarified changes in growth habit, elongation of plant height, and variation in heading date in 4 experimental plots, i.e., control, Iong day, short day (10 hours) in field culture, and normal culture in greenhouse as described in report 2. In this paper, we studied changes in growth habit, elongation of plant height, and variation in heading dates in 4 experimental plots ; control, 10ng day, short day (10 hours) in field culture, and normal culture in greenhouse, using the plants subjected to low temperature (O-2°C) treatment for 60 days and those not treated with low temper ature at the germinating stage. The results obtained are summarized as follows : 1) Varieties of erect type and those showing the prostrate type were different in their low temperature requirements at the seedling stage and there were varieties which required high temperature at young stage. Based on their behavior, we attempted to subdivide these varieties as follows: a. Varieties of erect type did not require low temperature at the seedling stage and the heading date was accelerated by either greenhouse culture or long day treatment (Shinchunaga and Norin 20). b. Among the 3 prostrate types, a variety belonging to the first type did not require low temperature at the seedling stage, but demanded long day for the change from prostrate to erect type in spring (Ceres). c. A variety belonging to the second prostrate type did not require low temperature at the seedling stage but needed high temperature, and it did not depend on long day for the change from prostrate to erect type (Wichita): ' d. Varieties showing the third prostrate type required both low temperature and long day fcr the changes from prostrate to erect type, and the effect of high temperature on the growth habit changes was mainly affected by day-light length (Pawnee, Norin 8 and Oinoue). Differences among the erect, prostrate, and medium types in their requirements for temperature and long day are shown in the following table. 2) Three kinds of prostrate type wheats seem to, be characteristic of the growth habit and the prostrate type appeared not only by low temperature but also by unfavorable environmental conditions. However, once after the prostrate type was changed into the erect one, the latter type did not change back to the prostrate type by unfavorab e environ mental conditions.

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The data used m this study were obtained from Corriedale yearling ewes raised at the Department of Animal Husbandry, Hokkaido National Agricultural Experiment Statich during 7 years from 1951 to 1957. They were analyzed to determine the genetic, environmental and phenotypic correlations among the following four economic characters, body weight before and after shearing, greasy fleece weight and staple length. The *-orrelations among paternal half-sibs were used with the records of 283 yearlin, g ewes. The correlations among paternal intra-sire were used with 206 pairs on which records were available on both the daughter and dam. Heritabilities estimated from paternal intra-sire correlations were 0.41. 0.55.0.35 and, O.37 for body weight before and after shearing, greasv. fleece weight and staple length, res pectively. When correlations were estimated among paternal half-sibs, genetic, environmental and phenotypic correlations between body weight before shearing and other characters ; body weight after shearing and greasy fleece weight showed middle or high values (near, O. 55-0. 72), and correlations between body weight after shearing and other characters ; staple length and greasy fleece weight showed low values(near O.20-0.37)with the excepticn of positive high genetic correlations (near O.74) between the first and staple length. Also correlations between staple length and other characters; body weight before shearing and greasy fleece weight showed pcsitive low (near O.17-0.26) and middle values (near O.43) with the exception of positive very low genetic correlations (near O.004) between the first and body weight before shearing. When correlaticns were estimated among intra-sire, genetic, environmental and phenotypic correlations between body weight before and after shearing showed positive middle or high values (near O.64-0.75). Also each genetic correlation among characters 'with the exception of correlations between above two characters showed positive middle values. (near O.41-0.45).

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The data in this study are obtained from Corriedale yearling ewes raised at the Department of Animal Husbandry. Hokkaido National Agricultural Experiment Station during a 7-year period from 1951 to 1957. The indices for selecting yearling ewes are developed. These contain one or more of the three characters studied - body weight before shearing, greasy fleece weight and staple length. Each of the indices is directed toward selecting for the same aggregate genotype containing the genic values of these three characters. The genic values of these three characters are weighted by their respective relative economic values. The correlations between indices and aggregate genic values are nearly the same values for the indices including three or two characters except the staple length. Expected genetic changes in the means of the population selected on different criteria of selection are compared. It is evident that when threecharacters are selected at the same time the efiiciency of selection based on the index will be greater than selecting by any one of the characters involved in this study.

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In order to determine what proportion of diploid and tetraploid plants would produce, by open-pollination, as many triploid seeds as possible from mixplanting of diploid and tetraploid plants, 3 plots, each of them representing the ratios of 1(2x) : 1(4x), l(2x) : 3(4x) and 1(2x) : 8(4x) were laid out. The amount of triploid seeds differed among the 3 plots. The total number of triploid seeds obtained was highest in the plot with mix-planting ratio of l(2x) : 3(4x), but their percentage of the total number of tetraploid plus triploid seeds was highest in that of 1(2x) : 1(4x) ratio. The plot with mixplanting ratio of 1(2x) : 8(4x) gave the smallest amount and the lowest percentage of triploid seeds. When tetraploid plants are exposed to open-polliation in the field, mixplanting of dip-loid and tetraploid plants will give the best results if their ratio is 1 : 3 respectively.

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[in Japanese]

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