PREVIOUS INVESTIGATIONS UPON PLANTS 63 



affected. Adventitious roots sprang from the epicotyl, and three 

 days after this the main root died. The intervention of three days 

 between exposure of seeds and planting seemed to make no difference 

 in the result. The effect of the rays decreased with the distance, 

 and apparently ceased at a distance of four centimeters. When roots 

 of Vtcta Faha seedlings 3-11 cm. long were exposed to rays from 5 

 mg. of radium bromide for five days, the roots near the radium tube 

 grew longer at night, and the portions lying back of the tip grew a 

 little to one side in the region of the radium influence. Growth 

 ceased on the fourth day. 



Seeds of Brasstca napus seemed specially resistant both to radium 

 and to X rays. Five days exposure with 10 mg. of the bromide 

 did not interfere with germination and further development. Swollen 

 seeds irradiated with the same mass of radium salt showed an accel- 

 eration of germination, but subsequently the rate of growth became 

 normal. Removal of the seed-coats of Brasstca did not make them 

 any more sensitive, for development of these seeds was normal after 

 they were exposed. Ten days' exposure to rays from 10 mg. re- 

 tarded germination and growth, and exposure for a longer time com- 

 pletely destroyed the power to germinate. 



Growth of both root and shoot of Vict'a was retarded by exposing 

 the vegetative points to the rays, and in this respect etiolated and 

 non-etiolated specimens behaved alike. The growth of callus on 

 wounds of Poftilus alba was retarded by the rays. 



Germination of the spores of Aspergillus niger was inhibited by 

 two days' exposure under the radium tube, and the mycelia that 

 developed near the tube did not fruit. Kornicke considered these 

 non-fruiting hyphae in a condition of " latent Hfe," an interpretation 

 which Dauphin had applied to spores of Mortierella which failed to 

 germinate while exposed, but did so after the radium was removed. 

 Dry conidia of Asfergilhis niger, irradiated for 1-4 days with 10 

 mg. of the bromide, did not lose their power to germinate, though 

 the germination was more or less delayed according to the length of 

 exposure. 



London's*^ experiments indicate that the vitality of bacterial 

 cultures was destroyed after an exposure of two days to the 

 " emanations."* 



* See footnote, p. 8. This word is doubtless not used here in the sense of 

 emattatton, as defined bj Rutherford, but as a collective term, referring to all the influ- 

 ences from the radium, especially the rays. 



