EFFECTS OF RADIUM RAYS ON PLANTS 991 



and Gager (26) called attention to the importance of this fact in connec- 

 tion with the medical use of radium, especially in the treatment of cancers 

 and tumors, whose growth might possibly be promoted instead of retarded 

 under certain conditions of exposure to the rays. It was also pointed 

 out that, since cambium is specially susceptible to injury by radium rays, 

 no hope could be entertained of controlling the chestnut-blight fungus 

 [Endothia 'parasitica (Murrill) And.] by injecting radioactive solutions 

 into chestnut trees. 



The possibility that crop production might be increased by adding 

 radioactive substances to the soil, either with or without ordinary 

 fertilizers, naturally aroused considerable interest. Ewart's experiments 

 in Australia, in 1912, led him to the conclusion that a radioactive mineral, 

 known to accelerate the germination of wheat seeds, did not appear to 

 have any direct agricultural value, at least so far as wheat is 

 concerned. 



Experiments on the exposure of cultures of nitrifying and denitrifying 

 bacteria to the emanation from pitchblende led Stoklasa (78) to infer that 

 radioactive substances in the soil might increase fertility by promoting the 

 circulation of nitrogen. There followed a series of papers reporting tests 

 of the possibility of utilizing radium rays to increase crop production. 

 Sutton and Sons, of Reading, England, issued a leaflet in 1914, review^ed 

 in the Botanical Journal (October, 1914). They used radioactive ores 

 mixed in small quantities with the soil. They reported that by such 

 treatment the germination of rape seed was accelerated. The following 

 year Martin H. F. Sutton (86) experimented with tomatoes, potatoes, 

 lettuce, radishes, marrows, beets, carrots, onions, and several flowering 

 plants, exposing the planted seeds to gamma rays given off by about 

 0.00025 mg. of radium bromide in glass bottles inserted in the soil. The 

 results led to the conclusion that gamma rays, under the conditions of 

 the experiments, tended to inhibit plant growth. 



Ross (67) reviewing in 1914 the published results of experiments to 

 test the value of radioactive substances as fertilizers, closed his summary 

 as follows: 



Evidence is given to show that the action of uranium on plants is due to its 

 chemical properties rather than to its property of being radioactive, and that 

 the conflicting results obtained with radioactive manure from different sources 

 is to be explained largely by the presence of uranium, and of such nonradioactive 

 constituents as soluble salts and free acids. . . . The radium present, on an 

 average, in an acre-foot of soil is about 100 times greater than is contained in the 

 quantity of radioactive manure commonly recommended for application to an 

 acre. 



At this period a "radioactive" fertilizer was being offered for agricul- 

 tural use by the Banque du Radium (Paris). Stevens (Stevens Indicator. 

 April, 1914, page 150) found that growth was accelerated only when as 



