REPORT 
OF A DISCUSSION ON THE ASCENT OF WATER IN TREES 
Held in Section K at the Meeting of the British Association, 
Liverpool, September 18, 1896. 
Mr. Francis Darwin read the following paper : — 
Within the last few years the problem of the ascent of water has 
entered on a new stage of existence. The researches which have led 
to this new development are of such weight and extent that they might 
alone occupy our time. It will be necessary therefore to avoid, as far 
as possible, going into ancient history. But it will conduce to clearness 
to recall some of the main stepping-stones in the progress of the 
subject. 
The two questions to be considered are: — (1) What is the path of 
the ascending water ? (2) What are the forces which produce the 
rise. 
I. The first question has gone through curious vicissitudes. The 
majority of earlier writers assumed that the water travelled in the 
vessels. This was not, however, a uniform view. Caesalpinus, 1583, 
seems 1 to have thought that water moved by imbibition in the ‘ nerves/ 
Malpighi and Ray held that the vessels serve for air, and the wood- 
fibres for the ascent of water. Hales 2 , who believed in the ‘ sap- 
vessels ’ as conduits, speculated on the passage upwards of water 
between the wood and the bark. Also 3 , that water may travel as 
vapour, not in the liquid state. In the present century Treviranus 4 , 
1835, held that water travelled in vessels; De Candolle, 1832, that 
the intercellular spaces were the conduits. In Balfour's Manual of 
Botany, 1863, vessels, cells, and intercellular spaces are spoken of as 
transmitting the ascending water. 
The change in botanical opinion was introduced by the great 
1 Sachs’ Hist, of Bot. (English Trans.), p. 451. 2 Vegetable Staticks, p. 130. 
3 Loc, cit., p. 19. 4 Sachs’ History. 
[Annals of Botany, Vol. X. No. XL. December, 1896.] 
