Assuming a pedigree of parent-offspring mating, recombination effect on homozygosity by descent is studied numerically. Taking into consideration two linked loci, formulae for generalized inbreeding coefficient and coefficient of parentage are shown. Under several initial conditions, resulting degrees of homozygsity by descent are calculated.

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Dose-response curves for root growth could be approximated by the same general function as for dry seeds. Correlation of the sensitivity between soaked and dry seeds was significant with soaking up to 24 hours. The change in the sensitivity with increase in soaking time from 1 to 6 hours and with drying-back of seeds showed high negative correlation to the sensitivity in dry seeds.

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Crossings were carried out between both subgenuses of Mentha in order to find out histologically the cause of the cross-incompatibility between them. Pollen grains could germinate on the stigma of the species belonging to other subgenuses and pollen-tubes could penetrate their style tissue. But both the germination of pollen grains and the elongation of pollen-tubes were somewhat restrained and pollen-tubes which reached the base of style diminished in number as compared with the case of crossing between species in the same subgenuses.

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Four strains of Japanese mint were collected as the wild type in Totiki Prefecture and Hukusima Prefecture. The number of chromosomes observed were 96 (2 n) in one strain as the same of the cultivated mint and 72 (2 n) in other three strains. The principal components of essential oils identified from four strains were mono-terpens like that of the cultivated mint, but menthol content in each strain was found too little to be utilized in oil industry.

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Although the protein of the chloroplast and mitochondrial membranes is the weak point against freezing, there is no varietal differentiation of the content and stability of its constituent against freezing. However, there is a clear varietal differentiation of the content of sugars in the tea leaf. Therefore, the present authors elucidated where sugar must be accurnulated in a cell to increase frost resistance according to the biochemical experiments and micro-autoradiographic observations of <14>^C-sucrose. From these results, it is evident that sugars are distributed in the cytoplasm of cells in the plant to increase frost resistance.

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Cytogenetical studies were made on the hybrid between V. amphicarpa 2n=10 and V. macrocarpa 2n=12 and its progeny. In the F₁, six parental chromosomes could be identified and various karyotypes were observed in the F₂ generation. It was presumed that four types were fertilized in the F₁ gamete and grew next generation from the karyotypes derived in F₂, and these gametes could be also deduced from the chromosome homogeneity of the parents and behavior of the parental chromosomes in the reduction division of F₁.

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In clarifying the structural mechanism of lodging resistance of soybeans, it was found that the indeterminate variety had a greater value of bending rigidity in the base of the stem, was less in change of the rigidity by planting rate, and had less moments by plant weight and external forces. Then, it was considered that the indeterminate variety had the growth system adaptable to solid planting with respect to the lodging resistant ability.

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Yield tests were made for fresh and air-dried stems, leaves and heads in 385 varieties of "Wangul" which contalns two specres Cyperus Iwasakii M. and C. glomeratus L. collected from all the parts in Korea. Then the examination was carried out to know how much the air-dried fiber and pith could be produced from the green stems of several varieties. As the result, the yielding differences between the two species and among the varieties in them were shown clearly.

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