PLATE I 



HISTOLOGICAL EFFECTS OF RADIUM RAYS ON LUPINUS ALBUS 



PAGE. 



Fig. A. Cross-section through a fibro- vascular bundle of the hypocotyl 

 of a seedling from seed exposed for 72 hours, before soaking, to 

 rays from radium of i,Soo,ooo activity. Experiment 27 . . 224 



B. Same as A. Section taken from another plant through a 

 fibro-vascular bundle ........ 224 



C. Cross-section through a fibro-vascular bundle of the hypocotyl 

 of a seedling from seed exposed for 91.5 hours, before soaking, to 

 rays from radium of 1,800,000 activity. Experiment 29 . . 224 



D. Cross-section through a fibro-vascular bundle of the hypocotyl 



of a plant from seed not exposed to radium rays. Experiment 27. 224 



E. Cross-section through the tap-root of the plant from which C 

 was taken. Experiment 29 ...... . 225 



F. Cross-section through the tap-root of a seedling grown from 

 seed not exposed to radium ....... 225 



All the sections luere taken from the same relative regions of 

 the hypocotyls and roots. 



