The Path of the Transpiration-Current. 
BY 
HENRY H. DIXON, B.A., 
Assistant to the Professor of Botany, Trinity College , Dublin , 
AND 
J. JOLY, D.Sc., F.R.S., 
Trinity College , Dublin. 
With Woodcuts 2-8. 
I N some recent investigations on the ascent of sap, we had 
occasion to reconsider the question as to whether the 
transpiration-current is transmitted through the lumina, or, 
as the supporters of the Imbibition-hypothesis maintain, 
through the walls of the conducting wood. Although, un- 
doubtedly, the weight of recent experimental work on this 
question is in favour of the view that the sap moves in the 
lumina, yet as some of the methods adopted in these experi- 
ments were not, as it appeared to us, entirely free from error, 
we did not consider it superfluous to repeat some of the older 
experiments, eliminating, as far as possible, sources of error, as 
well as to add some new ones of our own. The present paper 
is occupied with an account of these experiments. 
Tracing the course of the T ranspira tion- Curren t hy means of 
Precipitates. 
The first of the older experiments which we will discuss are 
those in which cut branches are supplied with a salt-solution, 
[Annals of Botany, Vol. IX. No. XXXV. September, 1895. 1 
