60 TRANSLOCATION IN PLANTS 



of the experiments. When such samples were taken, in 

 most cases there was a clear increase in nitrogen and ash 

 in both ringed and unringed stems, but there was a much 

 greater increase in the unringed stems. Since Clements 

 had no sample from unringed stems at the end of the 

 season, he has no evidence concerning the relative amounts 

 of movement through ringed and normal stems. The 

 increases he obtained over the original amounts were great, 

 it is true, but I am sure the increases in total nitrogen and 

 ash in the peach trees ringed before shoot growth started 

 (see p. 48) were equally great, yet in the check branches 

 the increases were still greater by at least 50 times. 



Clements also states that the ring will prevent formation 

 of new xylem, which is true if the rings are made only in 

 the early spring. In most of the experiments reported in 

 my 1923 paper, however, rings were made, partly for this 

 very reason, much later in the season, when much or all 

 of the new xylem had been laid down. 



Evidence directly contradictory to that of my own with 

 woody plants has been reported by Maskell and Mason 

 for cotton plants (1929a, 19306, and Mason and Maskell, 

 1931). They have found accumulation of nitrogen above 

 rings in excess of the amounts found in unringed stems, and 

 amounts below rings less than in similar regions of unringed 

 stems. This evidence clearly supports their contention 

 that nitrogen, perhaps in the form of nitrate, or even as 

 organic nitrogen if analyses of tracheal sap are a criterion, 

 is carried upward to the leaves through the xylem, is 

 perhaps there synthesized into organic nitrogen, and 

 retransported through the phloem to other parts. Whether 

 this contradictory evidence is due to a difference in kind 

 of plant used, or to some other factors cannot be settled 

 without further experimental evidence. Most of the data 

 of Maskell and Mason were obtained within 12 to 52 hours 

 after ringing, whereas in my earlier experiments with 

 woody plants, the time interval was much longer, ranging 

 mostly from 22 days to two months or more. In later 

 experiments with apple and Ailanthus, however, samples 



