84 



CARNEGIE INSTITUTION OF WASHINGTON. 



and the afternoon is generally weaker than the morning. Clouds, of 

 course, have a great effect on the violet intensity, while the reflection 

 from cumulus clouds seems to increase the values; the highest in- 

 tensities were obtained on days on which there was a ''tendency" 

 to cloud formation. 



Monthly means of per cent of oxalic acid decomposed in the photometer in one hour 

 under uniform conditions. 



TUCSON-DESERT LABORATORY (2,700 FEET). 



1911. 

 December 



1912. 



January 



February 



March 



April 



May 



June 



July (no record) . 



August 



September 



October 



November 



December 



1913. 



January 



February 



March 



April 



May 



June 



Morning Tempera- Cloudless tii„»;~.,™ x/r;-;™,,™ Afternoon 

 mean ture iSean. days. mean. M^^''^'""' M"*"""""- mean. 



14.44 



17.15 

 18.58 

 18.50 

 21.96 

 21.16 

 21.63 



19.89 

 22.61 

 21.51 

 15.76 

 15.71 



15.24 

 17.66 

 20.81 

 22.43 

 23.09 

 22.10 



25.4 

 25.7 

 28.0 

 33.0 

 34.9 

 42.1 



39.7 

 29.3 

 24.7 

 21.3 



20.9 

 23.5 

 26.5 



15.76 



17.22 

 18.72 

 20.43 

 21.99 

 21.82 

 21.95 



17.09 

 16 15 



15.10 

 17.66 

 21.03 

 21.63 

 23.13 

 22.10 



18.47 



17.76 

 20.38 

 20.84 

 22.30 

 23.43 

 22.70 



21.85 

 23.75 

 22.21 

 18.17 

 16.92 



17.25 

 18.05 

 22.18 

 23.63 

 23.79 

 22.47 



6.07 



16.85 

 17.27 

 13.90 

 20.81 

 19.05 



10.37 

 20.63 

 21.02 

 10 03 

 14.05 



12.30 

 17.00 

 18.82 

 20.39 

 21.96 

 21.31 



18.52 



16.24 

 21.40 

 18.85 

 14.76 

 13.56 



14.10 



MOUNT LEMMON (9,250 FEET). 



1912. 

 June. . . 



Acidity, Gaseous Interchange, and Respiration of Cacti, by H. M. Richards. 



During the winter of 1912-13 the main work consisted in the 

 analysis of gas samples obtained in Tucson during the previous sum- 

 mer. These samples were taken from closed flasks, in which joints of 

 cacti were exposed for definite periods under a variety of conditions, 

 and were carried to New York in glass containers sealed with dry 

 mercury. From the analyses of these a large mass of data was 

 obtained which has been calculated out and reduced by Miss M. E. 

 Latham, who has also made most of the analyses. 



Additional determinations of intramolecular respiration and tem- 

 perature effects on respiration were also made during the winter, 

 with the usual Pettenkofer apparatus to supplement and confirm 

 previous results. 



During the spring an apparatus was devised, somewhat modified 

 from that of Aubert and other workers, for the more accurate deter- 



