I9 2o] MAGNESS— INTERCELLULAR SPACES 315 



found that in general the increase in permeability per io° rise in 

 temperature varies from 1.3 to 1.8 times, averaging about 1.5. 

 These data are based on permeability to water, but there is no 

 reason for believing that gases would be fundamentally different. 

 The diffusion of gases in all probability is mainly a physical process, 

 and as such is relatively much less affected by temperature changes 

 than the chemical changes involved in oxidation. 



From a consideration of these relative effects of temperature 

 on oxidation and on permeability, it is apparent that the absorption 

 of oxygen and release of CO, are increased much more by a given 

 rise in temperature than is the tendency for oxygen to be supplied 

 to the tissues, and CO, to be given off from them. Consequently, 

 as the temperature is raised, the amount of oxygen in the tissues 

 becomes less and less, while the C0 2 accumulates correspondingly. 

 This continues until the third factor becomes effective, that is, the 

 difference of C0 2 and oxygen pressures within and without the 

 fruit becomes so great that equilibrium is again established. 



Significance of ratio 



No attempt has been made in this preliminary work to associate 

 the percentages of CO, and oxygen found with the processes taking 

 place in the fruit. The data presented, however, clearly indicate 

 the necessity of taking this factor into consideration in many types 

 of horticultural and physiological investigations. It should be 

 given attention in studies of the effect of temperature upon the 

 processes in plant tissues, for it is readily apparent that much 

 variation may be caused by the composition of the medium in 

 which these processes are carried on. Of special importance is 

 the application of studies of this type to the questions as to the 

 effect of wounding and various other treatments on the respiratory 

 processes in tissues. Finally, it is of prime importance to know 

 the composition of the internal atmosphere in studying the effects 

 of various gases, etc., on plant organs. Some work has been done 

 on the effect of various gases on fruits and vegetables in storage. 

 obviously it is essential in such work that the composition of the 

 interna] atmosphere be known. 



