193 



Mr. Taylor also spoke briefly of a recent visit to Alphano, 

 Warren Co., N. J., where a corporation is engaged in the exploi- 

 tation of the sediment of an inter-glacial lake, the old bed of 

 which is covered by a deposit of muck or humus, which is not 

 sour and yields a large amount of plant food. Mention was made 

 of the great phytogeographic interest of the spot, and a field 

 trip to the locality was suggested. 



The second paper was given by Prof. H. M. Richards on 

 "Respiration and Acidity in Cacti.'" 



In common with many other succulents cacti show a high 

 acidity. The acids present are considered to be malic or iso- 

 malic. It has been known that this acidity diminishes during 

 the day and increases at night. The maximum is just before 

 sunrise and the minimum at about five o'clock in the afternoon 

 when the temperature and light are lessening in intensity. In 

 comparison with the diurnal temperature curve with the cactus 

 joint that of the acidity is very nearly the reverse. But the fall 

 in acidity is not due to a temperature effect alone, as is shown 

 by the exposure of the cacti to bright sunlight at a constant and 

 relatively low temperature when there is a marked diminution 

 in the acidity. In atmospheres with increased partial pressure 

 of oxygen the acidity diminishes more rapidly while in atmo- 

 spheres devoid of oxygen it usually remains stationary or even 

 increases. 



The highest acidity found was where the pure juice was 

 equivalent to nearly one fifth normal alkali. The greatest 

 extremes between day and night showed the acidity at its mini- 

 mum to be approximately one tenth of its maximum strength. 

 There ar.e considerable individual differences in different plants 

 and the range of acidity is by no means always so great. Long 

 joints still bearing leaves showed the highest acidity. Old turgid 

 joints differed very little whether one, two, or three years old. 

 Old flaccid joints showed the lowest acidity. 



The respiration is naturally greatly affected by the rising 

 temperature. It is highest at between 45° and 50° C. after which 

 the CO2 evolution gradually falls off and practically ceases 

 above 60° C. The evolution of CO2 after the maximum may 



