384 BOTANICAL GAZETTE [MAY 
(8) Inserting the deionizing tube (p. 382), the other conditions 
were the same as in 7. The experiment ran from May 28 to 31. The 
results are given in table VIII and fig. 9. Here the rate shows a 
very much more regular increase. ; 
(9) In order to determine whether the daily variation in carbon 
dioxide evolution was restricted to plants or whether it took place 
also in animals, an experiment (p. 383) was made with ten beetles,” 
placed in flask R on fine asbestos fiber soaked in water. Twice dur- 
ing the course of the experiment 2cc. of water were run onto the 
asbestos. To all appearances, the beetles behaved perfectly nor- 
mally during this time. The experiment ran from June 3 to 6. 
Day rate 
The results are given in table IX and fig. ro. Night pate. 1.099. 
Discussion 
ee : day rate aoe 
Although it is difficult to derive an exact ay Te" ratio with 
night rate 
material in which the respiratory activity is rapidly rising or falling, 
the following in a sense summarizes those of the foregoing exper!- 
ments which ran for a longer time: 
a Day rate , Day rate prnee ya 
Material Night rate normal air Night rate deionized air 
NNOR i ee ea PeI5O ee ee ee 
Wheat 5 cra I .042 1.010 
WR ei ered I.OQ1 1.014 
HOCUS. 4 ice. 1000) 6 hs es 
There is at present no satisfactory explanation of these facts. 
The phenomenon of atmospheric ionization is undoubtedly exceed- 
ingly complicated, and perhaps at first glance far removed from 
our present conceptions of climatological factors of physiological 
importance. However, in view of the fact that ionization 
the atmosphere is indicative of important chemical changes in 
the gases of the atmosphere, a physiological response to these 
changes is at least to be expected. These chemical changes, N° 
doubt, are of such a nature as to affect the valency or activity of 
the atmospheric gases, in this case more especially the oxygen. 
* The material (Le ptinotarsa ro-lineata) was kindly loaned by Mr. JOHN SINCLAIR, 
in charge at Tucson of the investigations of Professor W. L. TowER. 
