ANAEROBIC RESPIRATION 65 



oxygen.* On the other hand, anaerobic respiration occurs 

 very seldom under natural living conditions, as is evident from 

 the preceding statements. In what manner could a rarely occur- 

 ring process attain the standing of a widespread phenomenon of 

 adaptation? Finally, it is to be taken into consideration that 

 plants do not die instantly without forming CO.. The energy 

 value of anaerobic respiration often appears to be so insignificant 

 that no biological usefulness can be granted to it. It is ques- 

 tionable whether the scanty gain of energy supplied by anaero- 

 bic respiration can delay the death of the plant even for a short 

 time. 



On the basis of this analysis it may be concluded that the 

 conception of anaerobic respiration as an adaptive phenome- 

 non merits no consideration at present. Even at the start this 

 assumption was a downright abstraction. It relied on no 

 experimental evidence and contradicted some of the best-known 

 facts. 



4. ANALYTICAL METHODS FOR THE DETERMINATION OF 

 ANAEROBIC RESPIRATION 



The determination of the carbon dioxide liberated in the 

 course of anaerobic respiration is carried out by the use of the 

 same methods which were described for the determination of 

 oxygen respiration. The plants might be either left in the 

 current of an inert gas or confined in appropriate, air-tight 

 containers with the oxygen excluded. Absorption vessels for 

 CO2 which have already been described are used in the first case. 

 Care has to be taken that the absorption tubes for weighing, 

 such as potash tubes, absorb no alcohol vapor whereby con- 

 sideiable errors could appear in the analyses.^ The devices 

 required for this purpose will be discussed in the description of 

 the determination of alcohol. If closed vessels are used as 

 plant containers, the CO2 is determined by analysis of test 

 portions of the gas. This method is to be recommended partic- 

 ularly for experiments in which, besides the determination of 



I It is also essential to replace the inert gas in the potash tubes and soda lime tubes with 

 air before weighing. 



'' An apparent exception is that of Elodea according to a few experiments by 

 Lyon (J. Gen. Physiol. 6: 299-306. 19.23-24). — Ed. 

 5 



