The following relation between h, pitch of a twinning plant and r, radius of its cylindrical support explains our experiment which was made more extensively than that of previous report, h=a log r+b where a and b are constants. The characteristic radius of a twinning plant has nevertheless a meaning as far as the thickness of the support is small. Using the various plants we obtained the following values besides the corrected values of the characteristic radii of the plants formerly experimented. The formula used is h=2π(r(ρ?r))^1/2 We observed also the effect of the solar intensity as well as that of the degree of the dilution of the culture-solution upon the length of the pitch.