. Effects of the rays of radium on plants . Fig. 62. Experiment 91. Absence of Geotropic Response (Pot 27) in Shoots of Zea Mays following Exposure of the Grains, before Planting, to Radium Rays: 45 exposed to Radium of 1,500,000 X ; 27 and 24 to 1,800,000 X- Cf. figure 14. After 24 hours 5 of the 7 exposed seeds were found to have curved geotropically, and 7 of the 8 control seedlings. The experiment was repeated, using 6 germinated pea seeds under each bell-jar. After 24 hours all of the seeds showed posi- tively geotropic curvatures in both cultures (except one seedling in the control jar w
. Effects of the rays of radium on plants . Fig. 62. Experiment 91. Absence of Geotropic Response (Pot 27) in Shoots of Zea Mays following Exposure of the Grains, before Planting, to Radium Rays: 45 exposed to Radium of 1,500,000 X ; 27 and 24 to 1,800,000 X- Cf. figure 14. After 24 hours 5 of the 7 exposed seeds were found to have curved geotropically, and 7 of the 8 control seedlings. The experiment was repeated, using 6 germinated pea seeds under each bell-jar. After 24 hours all of the seeds showed posi- tively geotropic curvatures in both cultures (except one seedling in the control jar which became injured), but the radicles exposed to the emanation have grown slightly more than those of the control. Exposure to radioactivity as described appears to have no influence on geotropic sensibility, so far as can be detected by observing the growth curvature. The response, however, being a function of growth, may be varied according as the rate of growth is modified by the rays. To further test the effect of the rays on geotropic response, 5 un- soaked grains of " Hickory King" corn {Zea Mays) were exposed in contact with the sealed glass tube of 10 mg. of radium bromide of 1,800,000 activity for 12 hours. Eight days after the exposed seeds had been planted in soil, they showed less than one half the growth in length of control seedlings, and two of them had failed to grow erect, and lay horizontally over the surface of the soil. They were perfectly turgid and hence failure to keep erect could
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