IRON AND ALUMINUM SALTS ON CLOVER SEEDLINGS. 129 



to the arresting of the development or kilhng of the cells in the growing 

 l)ortion of the root, and not to a poisoning of the entire root system. 

 This is further shown by the large number of short roots which develop 

 from the base of the stem and grow until they touch the toxic solution. 

 The continued growth of the tops after the roots have become stunted 

 also seems to point to the fact that the injury was confined to the growing 

 tips of the roots. If internal, the tops would show the effects sooner than 

 from four to six days after the effect is noticed on the roots. The reason 

 the seedlings finallj^ die is due to a lack of nourishment rather than to a 

 poisoning of the seedhng itself. Finally, as Mr. Morse has shown in the 

 preceding article, no appreciable increase in the amount of iron is found 

 in the roots or tops of clover plants whose poor growth in comparison 

 with normal clover plants is assumed to be due to the toxic action 

 of iron. 



