PLATE 3 



HISTOLOGICAL EFFECTS OF RADIUM RAYS ON PHASEOLUS VULGARIS 



PAGE. 



Fig. A. Cross-section through the epicotyl of a seedling grown in soil 

 from seeds exposed, unsoaked, for 24 hours, to rays from a Lieber's 

 radium-coated rod of 10,000 activity. Experiment 1 1 . . 227 



B. Cross-section through the epicotyl of a seedling (a control 

 plant of Exp. 11), grown in soil, and of the same age as that from 

 which A was taken, but from a seed not exposed to radium rays . 227 



C. Cross-section through the upper part of the hypocotyl of the 

 seedling from which A was taken ...... 226 



D. Cross-section through the upper part of the hypocotyl from 

 which B was taken ......... 226 



E. Cross-section through the hypocotyl of a seedling grown from 

 seed exposed for 5 days (12 hours), during imbibition of water and 

 germination, to rays from a Lieber's radium-coated rod of 10,000 

 activity. Experiment 19 ....... . 226 



F. Cross-section through the hypocotyl of a seedling grown as 

 was that of E, but not exposed to radium rays, of the same age as 



the latter, taken through the corresponding region . . . 226 



