XXX 



THE EFFECTS OF RADIUM RAYS ON PLANTS 



A Brief Resume of the More Important Payers from 1901 to 1932 



C. Stuart Gager 

 Brooklyn Botanic Garden 



The discovery of X-rays by Rontgen in 1896 was followed in the same 

 year by Becquerel's discovery that the various salts of uranium possess a 

 hitherto unknown property of spontaneous radioactivity. After this 

 discovery, M. and Mme. Curie, of Paris, began to examine different 

 minerals containing uranium and found that of some 13 examined all 

 gave off what were then called "Becquerel rays." The Curies concen- 

 trated their investigations on pitchblende, the most active of the uranium 

 compounds studied, and in 1898 isolated -polonium and proposed the new 

 term, radioactive. Later in the same year appeared the epoch-making 

 paper by the Curies and Bemont announcing the discovery of radium. 



From that date to the present, there has persisted in physiological 

 circles an unfortunate misunderstanding as to just what radioactivity is. 

 Perhaps, therefore, it may not be amiss to state here that the element 

 radium gives off three types of radiation which penetrate objects opaque 

 to the rays of the solar spectrum. These are: the alpha rays (streams of 

 particles bearing a positive electrical charge), beta rays (streams of 

 electrons, bearing a negative charge), and gamma rays (a penetrating 

 type of X-ray). In addition to these three types of rays, radium also 

 gives off a chemically inert, radioactive gas. This is the emanation, 

 more recently christened emanium. The atom of the emanation gives 

 off only alpha rays. 



It was about three years after the discovery of radium was announced 

 before what is possibly the first paper appeared reporting experiments on 

 the effect of radium rays on living organisms. This was a paper by 

 Becquerel who reported in 1901 that an exposure of a week or more to 

 radium rays destroyed the germinating power of seeds of cress and white 

 mustard. Negative results followed an exposure of only 24 hr. The 

 experiments were made in Becquerel's laboratory by Louis Matout. 



Between Becquerel's pioneer paper and the year 1908, more than 100 

 papers were published reporting the results of investigations of the 

 effects of radium rays on living plants. Most of these papers were cited 

 and summarized by the writer in a memoir (25) on the Effects of the 

 Rays of Radium on Plants. This memoir was referred to by Richards in 



987 



