633 
the Ascent of Water in Trees. 
not fatal to Strasburger’s conclusions, is no doubt a serious criticism. 
For if 13 m. can be supported, some of Strasburger’s experiments are 
inconclusive. He finds that a branch can suck up a poisonous fluid to 
over 10 m., and, as above explained, argues that all ascent above that 
height, not being due to barometric pressure or to the living elements 
(since the wood is poisoned), is for the present inexplicable. But, 
if Schwendener is right, the effect above 10 m, may have been due to 
atmospheric pressure. Askenasy (loc. cit. infra, 1895, p. 6) objects to 
Schwendener that the supposed action cannot be continuous. By 
repeating the diminution of air pressure at the upper end, the move- 
ment of water becomes less and less, and sinks to almost nothing. 
Askenasy adds, moreover, that the amount of water which could 
be raised according to Schwendener’s theory would be very small. 
One difficulty about Schwendener’s theory is that the result depends 
on the length of the elements of which the chain is made up (such 
element being a water-column, plus an air-bubble). In his paper, 
f Ueber das Saftsteigen V he finds that the elements of the chain 
in Fagus equal in round numbers 0*5 mm. In his paper 1 2 , ‘ Wasser- 
bewegung in der Jamin’schen Kette,’ he finds the element in Acer 
pseudo-plaianus =0-9 mm., in Acer platanoides and Ultnus effusa — 0-2. 
But the calculation (1892, p. 934) is based on the existence of a chain 
in which the water-columns are each 10 mm. in length, a condition of 
things which he allows does not occur in living trees. 
But even if we allow Schwendener to prove theoretically the 
possibility of a Jamin chain being raised to a height much greater than 
that of a barometric column, I do not think he invalidates Strasburger’s 
position. Schwendener’s idea necessitates the travelling of a Jamin 
chain as a whole, i.e. the translation not only of water, but of air- 
bubbles. But this cannot (as Strasburger points out) apply to his 
experiments on Conifers, in which the movement of air to such an 
extent is impossible 3 . And for the case of dicotyledonous woods, 
Strasburger has shown that the movement of air is excluded by the 
fact that transverse walls occur in the vessels at comparatively short 
distances. In Aristolochia the sections may be as long as 3 m., but in 
ordinary woods according to Adler 4 we get: Alnus 6 cm.; Corylus , 
1 K. Preuss. Akad., 1886, p. 561. 
2 K. Preuss. Akad. Sitz., 1893, p. 842. 
3 ‘ Ueber das Saftsteigen,’ Hist. Beitrage, v. 1893, p. 50. 
4 As quoted by Strasburger. 
U U 
