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Notice of Book . 
matter. The method adopted was to inject pieces of the stem with 
mercury, under pressure, and to observe the length of stem through 
which the mercury could be made to pass, and the number of vessels 
through which it escaped, on the lower cut surface. The general 
result is that while the vessels vary much in length they are on the 
whole much shorter than De Bary and most anatomists supposed. 
Among the longest vessels are those of the Oak, which are often two 
metres in length, and some of which may even extend the whole 
length of the stem. This, however, is an extremely rare case ; in 
almost all plants the length of each continuous vessel is a mere 
fraction of that of the entire path of conduction. 
Of the physiological half of the work the greater part is devoted to 
the question of the ascent of water in the wood. A repetition of the 
familiar c ringing ' experiments was first undertaken, with the result of 
proving once more that only the wood conducts the water-current, 
and that in the wood only the living alburnum is functional. In spite 
of this latter fact the author, on the ground of experiments to be 
mentioned below, does not admit that living cells take any part in the 
conducting process. The non-conductivity of dead wood depends on 
its comparative dryness, not on the absence of living elements. 
Some general remarks on the whole question serve to define the 
author’s point of view, and to introduce the experimental work. Prof. 
Strasburger, having convinced himself that the water-current passes 
through the cavities of the tracheae, was at first disposed to accept 
the 1 vitalistic ’ theory, according to which the protoplasm of the living 
wood-cells, either by active contraction, or by its influence on osmosis, 
plays an essential part in pumping up the water. His experiments, 
however, have led him to the opposite conclusion, that the ascent of 
water in plants is a purely physical process, though one of which 
Physics is not at present able to give a full explanation. 
The author has certainly established a very strong case, and in 
the face of his experiment the theories of Westermaier and Godlewski 
no longer appear tenable. 
He summarises his results as follows (p. 539) : — That the ascent of 
water in the plant is a physical and not a vital process was first 
proved by experiments with plants more than 10J metres in height, 
which were caused to take up poisonous solutions. Corresponding 
results were attained with plants previously killed by other methods. 
The conditions necessary for the ascent of water are: (1) that the 
