The relationship between the number of primary roots and yield components was investigated by using the same materials as in the preceding study. The primary roots were distinguished as elongated and 'stunted' roots. Elongated roots were further classified into three types, A, B and C, according to their morphological traits. The data thus obtained were analyzed statistically on per-culm or per-'shoot unit' basis in the case of primary roots, and on per-culm basis in the case of yield components. In the case of analyses per culm, the total number of primary roots and the the number of elongated primary roots showed significantly high correlations with the number of spikelets and with the weight of ripened kernels. The result was similar to that obtained in the preceding study. Among the three types of elongated primary roots, the number of type A roots, which are thick and long-elongated type, were most correlative to the yield components. The relationship between the yield components per culm and the number of primary roots of each 'shoot unit' were examined on main culms and on tillers, respectively. In this case, the 7th 'shoot unit' of main culms or the corresponding 'shoot unit' of tillers was the most remarkable 'shoot unit'. The number of elongated primary roots, particularly the type A roots, of this 'shoot unit', was found to be most correlative to the number of spikelets or the weight of ripened kernels.
