152 
Laboratory Note. 
The filtering flask containing some peas, which have been 
previously well soaked in water to start germination, rests on the 
table. The strong,caustic potash solution is contained in a short 
wide specimen-tube, which is suspended by a loop of cotton from a 
bent pin stuck into the cork of the flask. The horizontal glass tube, 
connected with the side tube of the flask by a piece of indiarubber 
tubing, has its last inch or so bent at right angles, and dips into a 
dish nearly full of mercury supported on a wooden block. 
The absorption of the oxygen by the germinating peas causes 
the mercury to be drawn into the tube, whence it runs into the 
flask and collects at the bottom, lifting up the seeds which float on its 
surface, thus showing clearly that a considerable amount of oxygen 
has been taken from the air contained in the flask during respiration. 
The horizontal tube should slope very slightly upwards towards 
the flask to prevent any mercury running down into the flask by its 
own weight, and the level of the mercury in the dish should be kept 
only a little below the level of the side tube so that the mercury 
will require to be raised only a slight vertical distance. 
If a graduated glass cylinder with a side tube could be 
substituted for the filtering flask, the apparatus might be employed 
for rough quantitative work. The objection to using an ordinary 
graduated glass cylinder and bending the proximal end of the 
mercury tube at a right angle so that it might pass through the 
cork closing the mouth of the cylinder, would be that the difference 
of level between the extremity of the tube inside the cylinder and 
the level of the mercury in the dish outside would cause this tube to 
act as a siphon when the mercury began to run into the cyliuder. 
On the other hand, if one tried to avoid this happening by 
keeping the mercury in the dish at a slightly lower level than the 
opposite extremity of the tube, a negative pressure sufficient to 
affect seriously the result of a quantitive experiment would be 
required to raise the mercury in the tube. 
A. W. BARTLETT, M.A., B.Sc. 
Botanical Department, 
Sheffield University. 
