3. No stimulation from X‑rays or gamma rays.

Various workers have reported at different times preliminary data showing stimulation of slight amounts of radiation. Most, if not all, of these reports are based on limited data and, so far as we are aware, no extensive experiments have corroborated these preliminary indications of stimulation.

Last summer an experiment was planned to determine any stimulating effects of X‑rays and gamma rays. The X‑ray used was set at 160 KV and 10 m.a. Doses given were 250, 500, 1000 and 2000 r. Ccmparable doses of gamma rays were given by placing the seeds (in petri dishes) at a distance of approximately 1/2 meter from a 16 curie source of Cobalt^6O. Four different 4 x 4 latin squares were planted with seed given the four different dosages of X‑rays and gamma rays. In two latin squares standard early field corn was grown. In the other two short hybrids with the reduced gene (rd) were grown. These were used because it was thought small differences in height might be more readily detected. In all of the latin squares 4 row plots were planted, using a split‑plot technique whereby two rows were checks with no treatment and for two rows the seed was radiated.

Height measurements were made at weekly intervals on one of the four replications of each latin square and total height was obtained on the mature plants of all plots. There was no significant difference in height of any of the 4 X‑ray treatments or the 4 gamma ray treatments in comparison with the controls. Likewise the yields showed no significant difference for any treatment. Experiments will be run in 1950 using doses of 2000, 4000, 8000 and 16,000 r of both X‑and gamma rays. On the basis of present information it seems unlikely that a stimulating effect will be found. Certainly none was found using doses of 250, 500, 1000 and 2000 r of either X‑rays or gamma rays. Neither was a depressing effect formed for any of the dosages used.

W. Ralph Singleton