( 571 ) 
and we cannot suppose that the circumstances which are changed 
in the operation, are altered exactly in such a way as to bring to 
light the observed regularity. Thus the distribution of pressure before 
death can only be explained on the assumption that there are pressor 
factors, i.e. pumping actions in the wood. 
This view receives important support from quite a different side, 
through the experiments of Zijlstra 80 ). He allowed a solution of 
Saureviolett to ascend living and dead branches and then examined 
them microscopically. In the living ones only the tori of the bordered 
pits were stained, together with a thin layer of the walls of the 
vessels; in the dead ones, however, the whole of the wood was 
coloured uniformly. It follows from this that the water current 
takes quite a different course in dead wood from that taken in 
living wood. 
That in the lilac only the one manometer was affected, which was 
attached to the portion killed by induction shocks, cannot in my 
opinion, be explained in any other way than by the aid of God- 
lewski’s theory. If one imagines, with Dixon and Jolt, that the 
whole trunk behaves like a dead tube, the phenomenon cannot be 
explained. An increase of resistance cannot be the cause, for then 
the other manometers would have undergone this influence. If on 
the other hand, we imagine a tree-trunk to be a system of tubes in 
which everywhere small pumps occur, the phenomenon becomes 
intelligible. The death of the piece of trunk puts the pumps out of 
action locally and the suction must there be somewhat greater to 
get the water through the piece of dead wood. This would not 
necessarily be observed at the following manometers, since the inter¬ 
mediate elements bring the pressure back to normal. 
I regard all the above as proof positive that the living wood has 
a hydromotory power. The experiment with Corrms already proves 
this very clearly: one could almost see the recovering intermediate 
portion suddenly begin pumping, as it were before one s eyes. 
After thus having given the positive proof that the living wood 
assists in the ascent of the water I will again take up the theoretical 
considerations with which I started, and see to what extent this 
proof can modify the condition of affairs. 
We encounter the difficulty that Strasburger’s intoxication experi¬ 
ments prove that help of living elements is not necessary, whereas 
the only theory which is not adversely affected by these experiments 
• becomes untenable on account of the pressure measurements. The 
solution is clear from the preceding. 
The adherents of Godlewski are wrong in asserting that water 
