( 565 ) 
leaves faded, prove that dead wood 
cannot transport enough water to 
balance the transpiration 17 ). 
4 a. The structure of the wood is 
in favour of Godlewski’s theory s2 ). 
they got a decoction of wood for 
their drink 18 ). 
46. “The very structure of the 
wood offers the strongest evidence 
against Godlewski’s theory” **)» 
Living wood offers the same 
resistance in either direction to the 
forcing through of water 20 ). 
5a. Arguments from analogy 2Z ). 
5b. Arguments from analogy n ). 
6a. The distribution of pressure 
in living transpiring trunks is op¬ 
posed to the cohesion theory ”). 
66. The measurements of pres¬ 
sure are considered unreliable or 
are left out of account. 
Point i. The question of the “continuity of the water-threads” 
in the wood amounts to the following. The cohesion theory requires 
the assumption that the water in the tree forms one connected mass 
from the root to the leaves. Every xylem vessel in which there is 
an air-bubble has according to this theory become useless for the 
conduction of water, for in such a vessel the water cannot be under 
negative pressure; it is at once sucked empty by the adjoining vessels. 
Every bubble of air therefore puts one vessel out of action. 
Now if it could be shown that by far the largest proportion of 
vessels contain air bubbles, only a small percentage would remain 
available for the conduction of water, and perhaps here and there 
the required connection of the water would be entirely interrupted, 
so that there could be no question of the cooperation of cohesion. 
It is of course difficult to prove the absence of air, for in the 
necessary manipulations preparatory to the examination there is always 
the chance that air bubbles in some way or other get into the 
vessels 24 ). If air is found in the majority of the vessels this does 
not prove that it was already present in the living plant, for it may 
have penetrated during manipulation. 
For the further course of my argument it matters little, however, 
whether Dixon and Jolt or whether their opponents are right on 
this point. I will not therefore discuss it any further. 
Point 2. The proposition, that physical forces alone are insuf¬ 
ficient ss ) to raise water higher than 13—14 metres is a very weak 
point in the defence of Godlewski’s theory, for Strasburger’s intoxi- 
38* 
