645 
the Ascent of Water in Trees. 
that I was led to believe that the branch did not absorb any water at, 
all from the apparatus, but merely exerted a tensile stress upon it. 
I am not now going to inflict upon you an account of the 
observations which I have already published ; I will merely state the 
conclusions to which they led. I was struck with the relatively high 
degree of suction-force which can be developed by a branch after its 
leaves have been removed ; and this led to the consideration that it is 
important to investigate the suction-force of stems quite independently 
of the leaves in the first instance. I cannot but think that hitherto 
the problem has been obscured, rather than otherwise, by introducing 
considerations based on the action, real or supposed, of the leaves in 
the development of the suction-force of branches. I would urge that 
it is of primary importance to study the stem, and to ascertain what it 
is capable of effecting by itself. 
In the second place, I was struck with a fact upon which Mr. Darwin 
has laid stress, namely that the suction-force of a branch is not 
essentially dependent upon the life of the branch. I found that if 
a branch be killed by the injection of sulphate of copper, it still can 
develop a very considerable suction-force. Now in a branch thus 
injected, the normal conditions of osmosis must be altogether upset, 
and yet water reaches the evaporating surface : hence osmosis does 
not appear to be an essential condition to the conduction. 
I now pass on to observations which I have since made. The 
logical outcome of the preceding considerations was to institute 
observations on dead leafless branches. For this purpose I used dead 
hazel-branches (which had served in the garden as pea-sticks during 
the summer); branches, that is, which, if I may so say, had died 
a natural death. I found that, in order to make satisfactory experi- 
ments with these sticks, it is necessary to previously inject them with 
water, and to cover all exposed cut surfaces with melted paraffin. 
In illustration of the results attained, I may mention that the best 
result was a suction-force of 19J inches of mercury developed by 
a piece of stick 1 8 inches long. This establishes the fact that a very 
considerable suction-force is developed by a branch independently of 
leaves or of life ; and this is a fact which demands complete 
investigation. The problem of the travelling of the transpiration- 
current is here presented in its simplest form. We have a small piece 
of dead branch, without leaves, without osmosis, developing a force 
which would probably suffice to raise a column of water to a height 
