To investigate the effects of internal radiation of various intensityon the test crop(flax), seeds of four levels of activity($15.5{ imes}10-4 $mu$c/grain, 9.0{ imes}10-2$mu$c/grain, 2.2{ imes}100$mu$c/grain and 3.8{ imes}10-1$mu$c/grain)$</TEX> which had been obtained by immersing them into various concentrations of P-32 original solution (total activity: 90 mc, To: 3/21) for 24 hours at room temperature, were germinated, transplanted later into pots, and the rate of germination and the successive growth were observed, and the inorganic conents of the plant top were analyzed. The results are as follows: 1. At the early stage of germination, the plants manifested themselves both inhibitory and promotive effects at higher and lower activity levels respectively, compared those of the control. These difference of growth on account of different levels of activity appeared, however, to be gradually narrowed in the course of time after germination, except at the highest activity. 2. Two weeks after transplanting, the plants of the lowest activity showed more vigorous growth than those of control. The plants belonging to the other activity levels on the other hand, tended to be less growing, the higher the activity. However, this growth gap between treatments seemed to be progressively closed one month after transplanting. 3. Most of the leaves and stems of the plants belonging to the highest activity level ($3.8{ imes}101$mu$c/grain$</TEX>) were withered during the early stage of growth, and this damage did not recover. 4. Practically no difference of growth was observed among treatments(excluding that of highest activity) one and half months after transplanting. 5. The fluorescence tended to be mroe delayed than the control, as the activity decreased. 6. There was a tendency that the number of pods harvested were larger in the plants treated with P-32 than that of the control. 7. The proportion of fiber in the plants at harvest appeared to be larger at lower activity and smaller at higher P-32 concentration than that of control. 8. As for the inorganic contents of the plant top harvested the floowing tendency was observed: (1) Nitrogen content was highest at the highest activity level at which the poorest growth ensued. (2) There was no clear difference of phosphorus content among treatments. (3) The contents of potassium and magnesium were higher than control at the medium levels of activity. (4) Calcium content of all treated blocks was found to be more than that of control.