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LABORATORY NOTES 
A Simple Respiroscope 
By SYDNEY MANGHAM 
T his apparatus can be put together easily from common labora¬ 
tory glassware, and has some advantages over certain other 
forms in use, e.g. that figured in Darwin and Acton’s Practical Plant 
Physiology. 
A glass drying tower forms the receptacle for the experimental 
material, e.g. germinating peas, which may be enclosed in a loose 
muslin bag suspended by a thread or supported by the constriction, 
or the peas may be allowed to rest on a perforated partition placed 
above the constriction. The top of the tower is fitted with a rubber 
stopper having two holes, through one of which is passed a ther¬ 
mometer, and through the other a short piece of glass tubing 
attached to a few inches of rubber tubing provided with a spring 
clip. In the base of the tower is placed some strong KOH (or water 
as a control), and the side tubulure is fitted with a rubber stopper 
connected by glass and rubber tubing to the narrow end of a gently 
sloping burette of the pinch-cock type. The lower end of the burette 
rests on the edge of a vessel of water and is provided with a length 
of rubber tubing which dips down into the water. All the rubber 
connections must be airtight and should be coated with wax. 
To start an experiment release the clip and suck up water to 
a convenient point in the burette, the graduated side of which should 
be towards the observer. Although the meniscus is very curved it 
will be found that a sufficiently good reading can be obtained 
without difficulty. A sheet of some opaque material should be 
wrapped round the tower if green tissues are used. 
The apparatus gives rapid results owing to (i) the suspension of 
the material above the KOH, (2) the large surface of KOH available 
for C 0 2 absorption, (3) the small difference in level between the two 
ends of the burette and the correspondingly small back pull exerted 
by the water column. 
