THE 
JOURNAL 
OF THE 
EOYAL HORTICULTURAL SOCIETY 
OF LOHDOK 
I. On the course of the Sap. By Andrew Murray, F.L.S. 
[First Paper, read to the Scientific Committee on 17th January, 1877.] 
A great revolution has of late years taken place in the ideas of 
vegetable physiologists regarding the course of the sap ; and, what 
is very unusual, it has taken place silently, and with scarcely any 
discussion. One regrettable consequence of this has been that those 
who are out of the current of scientific unwritten opinion remain 
in ignorance of the change that has been coming over men’s minds ; 
and even those who are in the midst of it are sometimes in doubt 
what the verdict of the scientific world is. That this is so will be 
admitted by those who attended the Botanical Congress at Brussels 
in May last, where this question formed one of the subjects selected 
for discussion, and elicited much diversity of opinion; and that a 
like uncertainty still prevails here may be seen from the pages of 
more than one of our horticultural periodicals. 
The old theory, as every one knows, was that the plants had a 
circulation similar to that of animals; that in the course of this 
the sap described two courses, an ascending and a descending one— 
the ascending course to the leaves, where it was submitted to 
certain influences which fitted it for the nutrition of the plant; the 
descending one from, the leaves, in a condition fitted for that pur¬ 
pose. The modern view, or, if I may not say that, at least 
the view which has forced itself so strongly on my mind ever 
since Mr. Herbert Spencer’s experiments that I have come to 
believe that every one must be of the like opinion, is that 
the sap describes only one course, viz., that from the root 
to the leaves, being drawn up by the power of the sun and other 
VOL. v. a 
