MURRAY ON THE COURSE OR THE SAP. 
7 
It held perfectly, and no escape of the liquid took place. After the 
cup was properly luted to the stem with tallow I cut a nick in the 
stem a little above the fitting, and then filled the cup with the 
lithiated litmus-mixture, so as to cover the nick. I then allowed 
it to remain on for six weeks, constantly renewing the mixture 
in the cup as it disappeared. 
After the expiration of six weeks I took up the plant and 
examined it; and here let me see that the Committee and I are in 
accord as to what I should have found had Sachs’ theory been well 
founded. I imagine that on the ordinary principles of gravitation 
I should have found the vessels below the nick filled with the in¬ 
fusion in consequence of its descent. So far as regarded that part 
of the plant it was no longer a closed tube, and there could be no 
ascent, but being, as it were, merely an open tube, whatever was 
poured into it should simply find its way to the bottom. And so in 
fact it did—the infusion below the nick descended to the very fibrils 
of the roots. In like manner, the part above the nick being a 
closed tube—closed by the liquid in the cup at the bottom and by 
the leaves acting as a sucker at the top—we should expect that the 
infusion would ascend : and so it did, just as it descended 
below the nick. But how as regards the parts that were on the 
opposite side from the nick ? According to Sachs’ theory, whether 
you call it the result of metastasis or of endosmose and exosmose, 
the infusion should have been found extravasated and infiltered 
through that side, both above the nick and below the nick and up 
the ascending branches, and everywhere a little; but in point of 
fact there was not the slightest extravasation nor a solitary par¬ 
ticle of lithia or litmus in any of these places. The depth of the 
nick was the measure of the extent of the penetration of the in¬ 
fusion, and it was as sharply defined as a line could be ; and this is 
just what I said should be the case. 
I said that the rapidity of the current would prevent any inter¬ 
mingling of ingredients by endosmose or exosmose, just as a small 
boat finds a difficulty in getting into the current of a heady river, 
even with the external aid of oars, or a small stream pouring with 
the force of gravitation into a more powerful one is shoved aside 
and driven down the banks. A particle of sap has neither oars nor 
gravity by which to force its way from one part of the ascending 
current to another, and it must be content to go with the flow of 
that part of which it is a component particle. At night there can 
be no ascending current, for the force that produces it, the sun, is 
withdrawn, but the tube is full and in equilibrium. 
