1963 年 13 巻 4 号 p. 151-156
A survey of the spatial distribution of the rice plant infected by the yellow dwarf virus was made on three paddy fields, the percentage of virus infection being low on No. 1,middle on No. 2,and high on No. 3,and the result obtained was examined from statistical point of view. 1) Distribution of infected plant per quadrat did not fit the binomial distribution when the infection was low and middle, but showed overdispersion. In these cases, the distribution was well approximated by the negative binomial. 2) Effect of quadrat shapes on the distribution pattern of infected rice plants was examined by means of the index of dispersion (s^2/x^^-). When a fixed number of plant was examined in a sample unit, sampling along a line in right angles to the row gave the least value of the index of dispersion. 3) According to I_B-Index, presented by MORISITA (1962) for discribing dispersion of individuals, it was clear that the larger the quadrat size, or the higher the percentage of infection, the less grew the intensity of overdispersion, and the distribution approached the random distribution.