240 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 



cases until the seed was mature. Throughout the experiments the 

 usual precautions of pedigree-culture methods were followed, such 

 as guarding with bags during pollination, and sowing in soil previ- 

 ously heated sufficiently to kill all seeds it might contain. f 



Seeds gathered in September, 1906, after the various treatments 

 described, were planted in soil in the propagating house, some in 

 late September or early October, others in late January or early Feb- 



Fk9. 69. Oiiagra biennis. Asymmetrical Rosette. The Ovary was exposed before 

 Pollination for four Days to the Rays from a Radium-coated Rod of 10,000 Activity ; 

 Pollen not exposed. Cf. figures 67, 68, and 70. 



ruary, 1907. In no instance was germination completely inhibited 

 by the radium treatment; that is, there was no case observed of fail- 

 ure of any considerable number of seeds to germinate. The per- 

 centage of germination seemed unaffected in any instance, though 



tSee Shull,i3p. 256. 



