58 TRANSLOCATION IN PLANTS 



of water is independent of the movement of nitrogen. 

 He found that in straight-grained trees, where roots and 

 branches are well distributed around the circumference 

 of the trunk, the sugars from the leaves on one side move 

 chiefly to the roots directly below them, and that nitrogen 

 absorbed by the roots on one side of a tree moves principally 

 to the branches directly above. Since cutting the roots 

 on one side diminished the growth of shoots on the opposite 

 side as well as directly above, probably because of decreased 

 water supply, and defoliation of one side increased shoot 

 growth on the opposite side, probably because of increased 

 water supply, it seems that water moves rather freely 

 from one side of the tree to the other. This evidence, 

 though not very conclusive, tends to support the suggestion 

 that water and mineral salts move independently from the 

 roots to the leaves. Other evidence of a somewhat similar 

 nature is presented by MacDaniels and Curtis (1930). In 

 this work spiral rings passing twice around the trunk were 

 made on a large number of apple trees. Sodium nitrate 

 was added to the soil and it was found that the nitrogen 

 had followed the spiral and then moved up vertically 

 after it passed the end of the spiral ring. The branches 

 on the side that was obstructed by the end of the spiral 

 received very little nitrogen, and behaved like branches that 

 had been completely ringed. That the nitrogen was 

 moving through the phloem, and not the xylem, was indi- 

 cated by the fact that the response was the same whether 

 the phloem only was removed in a spiral, or the phloem 

 and the xylem to a depth of two annual rings were removed. 

 Of course, by the end of the season new spiral layers of 

 both phloem and xylem were formed, and the nitrogen 

 may have followed these, but since the vertical xylem under 

 the spiral phloem ring was intact for a part of the season at 

 least, the nitrogen, if it is carried in the xylem, should have 

 followed these vertical xylem tubes instead of moving in a 

 spiral. 



11. Evidence Tending to Contradict That Presented in 

 Sec. 10. — Clements (1930) has recently published data 



