Within-population selection was carried out for three generations, and Japanese Italian ryegrass populations increased dry matter weight but no plateau in selection was reached. Degree of inbreeding depression in small populations and heterosis in a synthetic population were investigated. Possibility of further improvement in the growth from autumn to early spring in Italian ryegrass was discussed.

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This series of studies aims at finding possibility of breeding high-yielding barleys from two-rowedXSix-rowed varietal crosses. As the first step to approach this problem, effects of the genes for two-rowed and six-rowed characters, V and v, and the chromosome segment around the locus, on 13 irnportant agronomic characters were investigated, using two-rowed and six-rowed isolines, which were developed by backcrossing or selfing methods. The results have indicated that all the characters investigated are affected significantly by the genes, V and v, and their linkage blocks. These characters are classified into three groups, according to the intensity of the gene, action of Vv, the effects of the other loci and the interactions between them.

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Possible roles of leaves and growing points in varietal differences of flowering time were examined by means of mutual grafting of 6 soybean varieties ranging from early to late. They were grown under either natural day length or various photoperiods. Recording of flowering time of the defoliated scions showed that production of fiowering stimulus (or stimuli) in leaves were mainly responsible for the varietal difEerences of flowering time. Although the varietal dif-ferences in the sensitivity of the growing points to the flowering stimulus were also significant, their role in determining fiowering time was not so much as in the production of the flowering stimulus.

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In 1969 an almost sterile hybrid (2n=14) between a short-day variety of 'Tossa' jute (=Corchorus olitorius; 2n=14) and a photo-neutral wild species, C, depressus (2n=14) was obtained. In F₃, approximately 80% of the plants were short-day and 20% photo-neutral suggesting that the latter character is probably recessive. A few F₃'s chosen at random for chromosome counts turned out to be tetraploids (2n=28) indicating that the F₂ parents of the F₃ population underwent chro-mosome doubling. While characters of the economic importance such as height and nonbranching habit were almost restored in the F₄ and the F₅, fibre qualities deteriorated in thern. Fibre qualities however improved in sorne backcross progeny. Further the recessive (?) character for photo-neutrality continued to segregate in F₄ and in F₅' The presence of a paracentric inversion throwing out the gene in the form of a fragment during chromatid bridge formation is suggested to be the cause for the non-fixation of the photo-neutral character in the progeny.

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Rhodohypoxis baueri is one of the newly introduced African bulbous fl. owers and is attractive with a plenty of star-like flowers. Hitherto, several cultivars with small fiowers have) been known as diploid (2n=12), and furthermore, extra-large flowering cultivars such as "Tetra Whlte" were presumed to be tetraploid. However, the author has confirmed firstly that the latters are triploid (2n=18), and has explained their morphological and cytological characteristics, compatin with those of the former diploids. Lastly, grades of self- and cross-incompatibilities in several cultivars were examined by seed-bearing abilities through self-pollination and inter-varietal crossin".

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Using the trisomics, the relationship between their types and linkage groups wereseven linkage groups. Besides, linkage groups of eight genes newly described weredetermined.

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