38o 
AMERICAN JOURNAL OF BOTANY 
[Vol. io, 
sample had more ash in the leaves of the ringed stems, there were no regu¬ 
lar differences between the unringed and the ringed stems. As no leaf 
areas were reported, no definite conclusion can be drawn as to whether 
the ringing had altered the actual ash content. 
It is very evident from the data presented in this paper that ringing has 
hindered the movement of nitrogen and ash constituents into the tissues 
above the ring. This has been found to occur in all the plants studied, 
including peach, cherry, lilac, and privet. Experiments were also tried 
with chestnut, maple, and pear, but these were done so late in the year 
that no increase of nitrogen was evident even in the check stems. 
Whether the results can be considered as proof that nitrogen and other 
mineral nutrients move up through the phloem and not through the xylem 
with the water, may still be open to doubt. It is very probable that the 
rate of transpiration is usually less from the ringed stems. If there is an 
actual mass flow of water in the transpiration stream without passing 
through filtering membranes, a flow as through a pipe in an ordinary water 
system, if nutrients are carried in this stream and the associated living 
cells do not remove them, then the rate of transpiration would, of course, 
influence the amount of nutrients reaching the transpiring tissues. So 
far as I am aware, however, nothing as yet has been published showing 
conclusively that there is such a “transpiration stream” in plants or that 
the rate of transpiration directly determines the amount or rate of nutrient 
movement to the transpiring tissues. The one preliminary experiment 
reported in table 7 would indicate that transpiration is not an important 
factor directly determining the distribution of nutrients. The data pre¬ 
sented by Muenscher (1922) give perhaps even better evidence that trans¬ 
piration does not directly influence the distribution of nutrients. Though 
his experiments were chiefly directed to determine the influence of trans¬ 
piration on the absorption of nutrients, they offer evidence that it does 
not influence nutrient movement after absorption, for, if the removal of 
nutrients from the roots were hastened by transpiration, this hastened 
removal should cause greater absorption for the plant as a whole and 
should reduce the ash in the roots, the absorbing organs. He found, on 
the contrary, that, when transpiration was altered by light and shade, 
plants with high transpiration rates showed an ash content of the roots 
distinctly higher than those with low transpiration, when measured as 
total ash or as percentage of dry or green weights, and an ash content of the 
tops somewhat lower in percentage but higher in total amount. Of course, 
in neither case do the ash contents indicate the amounts present in the 
conducting system. This high ash content in the roots is probably due 
to their increased content of organic matter, and, in fact, it is difficult to 
arrive at any definite conclusion with respect to the effect of transpiration 
on the distribution of nutrients in experiments of this type in which the 
organic content of the tissues is not under control. 
