PLATE 4 



HISTOLOGICAL EFFECTS OF RADIUM RAYS ON ZEA MAYS 



PAGE. 



Figs. A, B, D, E. Cross-sections through leaves of seedlings grown 

 from grains exposed, before soaking, for 27 hours, to rays from 

 10 mg. of radium of 1,800,000 activity ..... 227 

 C. Cross-section through the leaf of a seedling grown from a 

 grain not exposed to radium rays .... . 227 



