1892. J An Apparatus for Root Pressure. 213 
or a glass tube attached to the stem at its base by means of 
a rubber tube making with it a water-tight connection. The 
observations were recorded by marking upon the tube each 
hour to indicate the rise of water in the tube or by measuring 
it with a scale in the glass or on a strip of paper or wood be- 
hind it. The apparatus required frequent attention and was 
in no sense self-registering. The other methods used were 
modifications of these but in all cases frequent attention was 
required. 
The following self-registering apparatus is suggested: The 
base of the apparatus is about 1 by 3 feet and is supported by 
legs about 3 inches high. About 10 inches from one end and 
in the center of the base is erected a standard about 2 feet 
high and 4 inches in width. On the short end of the base and 
near the post is fastened a set of strong clock-work (the Seth 
Thomas ‘marine works” answer the purpose very well). The 
clock-work is covered with a box, and the end of a cylinder 6 
inches in diameter and 1 foot 10 inches high is fastened to the 
hour pinion by means of a pin passing through a hole in the 
end of the pinion and fitting in a slot in the end of the cylin- 
der. The top of the cylinder is held in place by a pin pass- 
ing through a support from the main pillar, and a hole in the 
end of the cylinder. 
Ans pee the large upright pillar is fastened a U-tube, about 4 an 
ich diameter, one end being nearly as high as the pillar and 
the other but half the height. The tube is filled with mercury 
to within about an inch of the top of the short arm. The 
eae of the plant is cut off near the base and placed in posi- 
‘on. An inverted U-tube is tastened to the stem in the 
usual way by means of arubber tube tied with wire while the 
— end of the U-tube is connected to the larger one in the 
ame way. The small U-tube is filled with water through an 
pening in the top. 
he cylinder is made of bright tin and is blackened by re 
he it slowly in the flame of a lamp or gas jet. 
the Stor consists of a light steel wire with a aie 
ais somewhat smaller than the diameter of the tube. This 
n the mercury. It is then at the top of the tube bent 
the it angles twice and allowed to extend to the bottom ? 
sec. a where it is again bent at right angles and the se 
Pin driy, pe fest against the smoked surface of the cylinder. 
Side be en in the pillar prevents the wire from turning to one 
Cause of the friction of its end with the cylinder. 
vol 
