﻿90 BOTANICAL GAZETTE [February 



under conditions which it is hardly possible to make identical, 

 the respiration is found constant. 



I had been but a few weeks at this work before irregularities 

 in my results, which I could not prevent, and often could not 

 account for — just such irreg'ularities as cast a suspicion on more 

 than one piece of work on respiration — made it very evident 

 that sound results on respiration are not to be obtained without 

 the same precaution in the use of parallel controls which is 

 regarded as indispensable in other fields of physiology. So far 

 as I know, the only work in which a real control has been used 

 in experiments on respiration is that of Moller,^^ whose apparatus 

 is in that respect more worthy of imitation than the widely fol- 

 lowed one of Pfeffer and Wilson/'' 



The apparatus which I have used is illustrated by the accom- 

 panying diagram i^fig. /). .The subjects of experiment are 

 submerged in water in a large can. In the early part of the 

 work, I used in place of this can a large stone churn, black 

 inside, with a turned wooden lid soaked in India ink, and plugged 

 the openings around the connections with cotton similarly 

 soaked; but I have since satisfied myself that the light in the 

 interior of the laboratory will not disturb the experiment if no 

 care at all is taken to exclude it from the can. The air comes 

 to both bottles of experiment material after the removal of all 

 CO^ by passing two towers of solid KOH and a solution of 

 Ba(OH)2. From each subject of experiment the air passes to 

 a bottle, in whose stopper are four holes, which serves admirably, 

 and without taking more than a minimum of room, as a switch 

 board. When the experiments were carried on at a much higher 

 ^ temperature than that of the room, these bottles contained 

 Hj^SO^ to prevent the dilution of the baryta water by distillation 

 from the experiment bottles. In the diagram the absorption 

 tubes are Winkler coils. I have used them and Pettenkofer 

 tubes about equally, and have no choice, except that with the 



39MOLLER, H., Ueber Pflanzenathmung. Ber. Deutsch. Bot. Gesells. 2 : 306-321. 

 1884. 



<° Pfeffer, W., Ueber intramolekulare Athmung. Unters. Bot. Inst. Tubingen 

 1:636-685. 1885. 



