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Hohe (wo vorher Saugen stattfand) Loft in das hier angebrachte 
Manometer hineinpreszt, wahrend oben in der Krone nnd insbesondere 
unten am Stamm weder Saugung noch Pressung stattfindet”“). 
It is remarkable that Dixon, in his review of the state of the 
problem in the “Progressus*’, does not at all refer to the ice experiments 
of Ursprung, nor to measurements of pressure, although he there 
considers at length and refutes much less important objections. 
Thus we have traced the causes of the remarkable phenomenon 
mentioned in the introduction. The partisans of Godlewski point to 
the measurements of pressure and maintain that Strasburger’s expe¬ 
riments are invalid, whereas Dixon points to Strasburger and is 
not concerned with pressure measurements. 
As will he seen the position is somewhat confused. In my opinion 
no advance can here be made along a theoretical road. Experiments 
alone can lead us out of the confusion. 
I think I am able to supply conclusive, experimental proof that 
the normal living wood is able to pump water actively. 
In order to give this proof I started from the following preliminary 
conception. If the irregularity of the results of pressure measurements 
is really caused by a pumping action of the living wood, this 
irregularity must at once disappear as soon as the experimental trees 
are killed or paralyzed. This was indeed found to be the case. 
Moreover, as soon as the trunk was dead the differences of pressure 
followed the same rule as would be expected to apply to a glass 
tube. When the conditions became unfavourable to evaporation, as 
in the evening and when rain supervened, the indications of the 
manometers approached each other more and more. At midday, in 
sunshine, on the other hand they differed more. This becomes 
intelligible, when we consider that a more rapid evaporation requires 
a stronger current; for a stronger current larger differences of pressure 
are however necessary, in order to overcome the greater resistances. 
First I will describe the experiments somewhat more in detail. 
Later I hope to publish the curves of the positions of the manometers, 
together with the result of a more extensive investigation of this 
subject. 
Of a ± metres high specimen of Sorbus latifalia, which divided 
a little above the ground into two almost equal, strong branches, 
one branch was left intact as a control; to the other I fixed above 
one another some U-shaped open mercury manometers, in the following 
manner. Some lateral branches were cut off from the main branch 
in such a way that a stump of 5 cm. length remained. A tube was 
slid over this stump, and to it the manometer was afterwards fixed 
