386 BOTANICAL GAZETTE [MAY 
enters, is as yet not definitely established; nor can the formation 
of carbon dioxide be attributed entirely to the oxidative action of 
the oxygen. We know, however, that the total rate of respiration 
is greatly influenced by the accumulation or removal of the end 
products of the first stages in the series. Even assuming, then, 
that the only function of the oxygen is the removal of these end 
products, as is maintained by many physiologists, the more rapid 
oxidation of these substances would result in an increased total 
rate, and hence increased total amount of carbon dioxide evolved. 
This higher rate of oxidation, and consequent greater carbon 
dioxide evolution during the hours of sunlight, could be accounted 
for by the increased “oxidative power” of the air during this time. 
That no increased respiratory activity can be obtained with the use 
of artificial sources of light (except possibly the quartz mercury 
vapor lamps) is but natural, for light from these sources has no 
influence on the atmosphere. 
The factors influencing atmospheric ionization should be briefly 
mentioned. Water vapor and high relative humidity have been 
found to decrease greatly the values; observations made at high 
altitudes usually show higher values than those made at about sea 
level. It is to be expected, therefore, that the respiratory activity 
in the arid and high regions, as, for instance, at Tucson, would be. 
higher and show greater day and night variations than in a moist 
climate and at sea level. 
Finally, it should be stated that the day and night variations 
as reported in this notice are not of great magnitude, and can be 
detected only by careful and rather prolonged experiments. The 
phenomenon is none the less important, however, when considered 
in its broader physiological bearing. The development of this 
hypothesis will naturally require many more experiments. Work 
is now in progress with still finer temperature regulations and on 4 
larger variety of plants and animals. It is my intention to make 
simultaneous atmospheric conductivity measurements, and to 
study the effect of air artificially ionized by means of Roentgen 
rays or radium. 
DesEerRT LABORATORY 
Tucson, ARIZ. 
