抄録
In order to elucidate the authors' supposition that the phenomenon of degeneration of some varieties might dccur even on such self-pollinating plant as rice or wheat, when propagation continued for long generation, they compared the degree of heterosis between inter-plant crossing and intra-plant crossing with three leading varieties, which appeared in different ages, namely Bantoshinriki(80 years old), Asahi (50 years old) and Norin No. 18 (10 years Old). The seeds. were abundantly obtained in bcth cases by hot water emasculation method. The experiments were repeated in two seasons. The comparative data concerning meangrain weight and yield are cornpiled in table I. The results obtained are summarized as follows : No significant difference was obtained in mean grain weight and data of heading, expression of heterosis about growth and yield, that is, plant height, number of tillers, Iength of leaf sheath and leaf blade and wei.ght of ears per plant were dif. ferent among three varieties, although they are not so distinct as observed in such cross-pollinating plants as corn or rye. It is concluded that the phenomena of haterosis more st, ronger in older varieties than in younger variety. Some consideration on the degeneration of variety is briefly discussed.
