UPWARD TRANSPORT OF NITROGEN 63 



probability. This is another of the many translocation 

 problems that await further investigation. 



In experiments with stems of Ailanthus, I have found 

 clear indications of a redistribution between the leaves of a 

 single branch. The nitrogen of the older leaves decreased, 

 while that of the younger leaves increased. A method 

 similar to that previously used (Curtis, 1923) and recently 

 extended and described by Denny (1930) as the 'Hwin 

 leaf " method was used. Ailanthus with its large compound 

 leaves, bearing ten to twenty pairs of well-matured leaflets, 

 was found highly suitable for determining absolute changes 

 in dry weight, fresh weight, and nitrogen content, as well 

 as for determining percentage changes of the various 

 components. 



The finding of a high nitrogen content in both bark and 

 wood above a ring, and its decrease below, would somewhat 

 offset the suggestion that the differences may be due 

 chiefly to a redistribution within the upper part. Even 

 if all parts above showed an increase in nitrogen, however, 

 and those below decreased, the criticism still stands that 

 roots and stems below the ring were abnormally starved 

 and would therefore lose much of their nitrogen to the 

 transpiration stream. 



In later papers (Maskell and Mason, 19306; and Mason 

 and Maskell, 1931) they have confirmed their findings 

 of an increase of nitrogen above rings and have found 

 that the total ash, as well as potassium and phosphorus, 

 behave in much the same way. In these experiments they 

 may not have heavily pruned or defoliated the lower part 

 of the stem just previous to ringing as reported in the 

 earlier paper, but no leaves were left below the rings so 

 the stems and roots were certainly deprived of carbo- 

 hydrates which would favor loss to the xylem. The 

 increase in nitrogen of the stems immediately above the 

 ring may have been partly due to stoppage of nitrogen 

 moving down, and partly to an effect of the increased 

 carbohydrate in causing a redistribution within the upper 

 part. Mason and Phillis (1934) found, in nitrogen- 



