964 BIOLOGICAL EFFECTS OF RADIATION 



and Simons (15) also working with V. Faba concluded that light doses 

 up to 5 H.E.D. cause stimulation, but above that retardation of growth 

 occurs. Their results indicate that a less sensitive plant, i.e., one which 

 is little affected by the rays, requires a greater dose for either retardation 

 or stimulation than a more sensitive one. Wheat, which is less ray- 

 sensitive than V. Faha, showed transitory stimulation with doses up to 

 200 H.E.D. These investigators conclude that the dose necessary 

 to cause stimulation is in an inverse ratio to the ray sensitivity of the cells. 



Altmann, Rochlin, and Gleichgewicht (1) observed that irradiation 

 of the bean, Phaseolus vulgaris, resulted in a transitory acceleration 

 of development. They report that the stimulation dose varies with 

 the stage of development, the dose for the dry bean lying between 6 and 

 12 H; for the two-day seedling, between 1 and 3 H. When Ancel (2) 

 repeated this experiment, however, it was found that the control lots 

 showed as great a variation among themselves as did the control and 

 irradiated groups. If Altmann, Rochlin, and Gleichgewicht had increased 

 their control lots, doubtless they would have obtained among them differ- 

 ences as great as they observed between the control and irradiated plants. 

 Ancel (4) concluded from her experiments in which she used large numbers 

 of control and irradiated beans, lentils, and wheat, that the so-called 

 accelerating action of weak doses of X-rays on the development of plants 

 does not exist. The chief cause of error made by some of these earlier 

 experimenters is that they have not taken into consideration the indi- 

 vidual variation of the seedlings. 



Komuro (29a) repeated the experiments of Yamada and Nakamura 

 who had obtained an increased yield of rice from weakly irradiated seeds. 

 He reported that the number of tillers in plants from soaked seeds 

 decreased proportionally to the dose given, that no positive stimulation 

 was apparent, and that the crop was not increased by irradiation. This 

 same investigator (296), in a second experiment conducted two years 

 later, concluded from his study of two pure lines of Oryza saliva that 

 acceleration of germination is obviously shown in seeds X-rayed in the 

 air-dried condition and that a dose of 5 to 10 H seemed to be the optimum. 

 An analysis of the data, however, shows that in half of the experiments 

 only 4 to 20 seeds were used in each lot. Very slight acceleration or 

 none at all was evident in the majority of the remaining experiments in 

 which 100 seeds were used. Komuro concluded that early growth from 

 irradiated soaked seeds was better than from controls, but his figures 

 show very slight differences between the average lengths of each lot. 

 In testing the influence of radiation on processes showing as much varia- 

 tion as do germination and growth, a large number of seeds should be 

 used and differences between average measurements in each group 

 should be sufficiently great because of the individual differences which 

 occur even between members of groups subjected to the same environ- 



