43 2 Vines . — The Suction- force of 
a mode of experimentation in which the conditions should 
more nearly approach the normal, would be one in which the 
water in contact with the cut-off branch was enclosed in an 
air-tight vessel, thus excluding the intervention of the atmo- 
spheric pressure. Moreover, in such a case, any measurements 
which might be obtained would have reference solely to the 
suction-force of the branch. In the first experiments, made 
last year, the air-tight tube, entirely filled with water, to 
which the branch or shoot was attached, communicated with 
a mercurial barometer as a means of measurement, the fall of 
the mercury in the barometer indicating the suction-force of 
the branch. By this means I obtained values for the suction- 
force, which were much higher than any I have met with 
recorded elsewhere. In these experiments I used the Cherry- 
Laurel (. Primus Laurocerasus) as representing woody plants, 
and the Sunflower (. Helianthus animus) as representing her- 
baceous plants : with the former I obtained as a maximum 
a fall of 320 mm. of the mercury in the barometer-tube, and 
with the latter a fall of 116 mm. I cannot, however, attach 
great importance to these results, as the experiments were 
few in number, for they had to be brought to an abrupt 
conclusion. 
This spring I resumed experiments on the subject, but with 
an important alteration in the apparatus, namely this, that for 
the mercurial barometer I substituted a Bourdon’s vacuum- 
gauge. The apparatus, as used, is represented in the ac- 
companying Woodcut 1, where a branch is attached to an 
india-rubber tube connected with one arm of a T-tube at B, 
the two other arms of which are respectively connected by 
india-rubber tubes with the gauge C, and with a glass tube 
leading into the water- reservoir A, The water-reservoir is 
closed by an india-rubber stopper, through which pass two 
glass tubes, the one of which is connected with the T-tube, 
whilst the other carries a small piece of india-rubber tubing at 
its free end, and can therefore be hermetically closed by 
means of a pinch-cock at a. In preparing for an experiment 
the branch is attached to its india-rubber tube under such 
