X-RAY EFFECTS ON GREEN PLANTS 965 



mental conditions. If Komiiro in his second group of experiments had 

 used more seeds and grown his plants to maturity, he would doubtless 

 have confirmed the results of his former experiment. Because of his 

 conclusion that the germination of air-dried seeds, which were steeped 

 in water 29 hr, after irradiation, was obviously accelerated, Komuro 

 believed that the practical application of roentgen rays in agriculture 

 would be possible and profitable if air-dried seeds were X-rayed and sent 

 to other places for sowing in the rice fields. Ancel (2a), on the contrary, 

 found with wheat and lentils that there was no increase in percentage 

 of germination with irradiation and that delay in placing the irradiated 

 seeds under proper conditions for germination caused fewer seeds to 

 develop. 



Geller (10), after examining results of experiments covering the 

 period 1910 to 1923, concluded that small doses of X-rays cause accelera- 

 tion of development while large ones produce a depressing action. The 

 effect depends on the species and condition of the plant, for some are 

 more affected than others and all are more ray-sensitive when growth is 

 active. Geller believed that there was no absolute ray dose for retarding 

 or stimulating plant growth since the effect is dependent on so many 

 factors. At the present time, the problem of possible stimulation is 

 still unsolved. Some investigators believe that they have demonstrated 

 stimulative effects with weak doses while other careful experimenters 

 have demonstrated either no effect or one which is harmful to the plant. 



Papers Published since 1924 on Stimulation and Retardation. — Brief 

 mention will be made of the investigations of others working since 1924 

 who claim to have demonstrated a stimulative or accelerative influence 

 of X-radiation upon grow^th. Arntzen and Krebs (6), using peas, found 

 that with light doses a stimulative effect could be demonstrated for the 

 first and, in some cases, for the second 24-hr. period after exposure. 

 This was followed by retarded growth. 



Iven (17) has seemed to confuse the acceleration following a retarda- 

 tion in growth of Vicia Faba seedlings with true stimulation. In the 

 earlier part of his paper, he states that his results agree with those of 

 E. Schwarz, Koernicke, and Halberstaedter and Simons who considered 

 weak doses as stimulative. Later, he refers to growth-acceleration 

 phenomena which appear within 10 to 20 days after treatment, after 

 which growth again becomes normal. The stimulating effect with 

 minimum doses, Iven concludes, is a passing one. From these state- 

 ments, it would seem that Iven is referring to an acceleration of growth 

 following a retardation, which is commonly reported after radiation, rather 

 than to true stimulation resulting in increased growth. He found that 

 germination of seeds was not hastened by the rays. 



Rivera (53) considered increased development of aerial buds following 

 irradiation as a stimulation. He reported also that roots seem to derive 



