44 GERMINATION 



of radium bromide was set one cm. above the central seed. 

 The seedlings grew up, but without any curvature, indicating 

 positive or negative *' radiotropism," and the only noticeable 

 effect was a slight depression of growth in those within 

 one cm. radius of the tube. As stronger preparations of 

 radium became available more definite retardations and 

 inhibitions were observed ; thus Gager, in an elaborate 

 report, noted a more or less complete inhibition in cell 

 activities in younger and especially embryonic tissues, with 

 a few exceptions. The action of radium through the soil, 

 however, was different ; germination and growth were 

 both accelerated, and the plants farthest away were stimu- 

 lated most. Acqua found that different plants, and even 

 different organs of the same plant, were differently affected, 

 the root system in general responding more markedly than 

 the aerial parts, and in his experiments being arrested in 

 their development 



" These and similar results naturally suggested that the 

 residues left after the extraction of radium, but still contain- 

 ing radio-active material, might have definite manurial 

 value, and it was not long before definite statements were 

 forthcoming. Baker claimed that increased yields of wheat, 

 and radishes had been obtained by mixing one part of radio- 

 active material . . . with ten of soil. It is true that 

 Stoklasa's results were negative . . . but this did 

 not prevent the introduction of radio-active fertilisers, 

 and the enterprising syndicates and companies concerned 

 were by no means loth to push their wares. These were 

 investigated by Martin H. F. Sutton, the experiments being 

 made with radishes, tomatoes, potatoes, onions, carrots, 

 and marrows, some grown in pots, others in plots out of doors. 

 Eight different radium residues were used, in addition to 

 pure radium bromide ; the dressings were so arranged that 

 the equivalent quantities of radium were given in each 

 case (l/400th gm. radium bromide to 15-lbs. of soil : 2| 

 times this amount per square yard to the plots). 



"In no case was there any clear evidence of increased 

 growth : even the pure radium bromide seemed to be with- 

 out action. 



