38 ACTION OF RADIUM ON GREEN PLANTS 



disintegration became visible in many cells simultaneously, and within 

 5 minutes after the disintegration began to be visible in a few cells, 

 practically all the cells in the vicinity of the radium were thus affected. 



In the dark, this phenomenon of disintegration commenced in 

 about one-fourth of the time; namely, after an exposure of from 35 

 to 70 minutes, the average being 45 minutes. 



Colonies of Volvox were exposed in a small glass tube in which the 

 radium preparation was placed. In the light, the colonies became 

 motionless in 2 hours; in the dark, the same condition was attained in 

 55 minutes. These periods represent the average of many trials. 



It is very evident that the life of the cell is prolonged by some con- 

 dition connected with photosynthesis; a more definite statemen: 

 cannot be made on the basis of these preliminary experiments. 



