28 



TRANSPIRATION IN A DESERT PERENNIAL. 



The atmometers used were No. 245, white, and a brown* one of the same 

 type, which was not numbered in the series, but is called No. 10 for conven- 

 ience. The white atmometer was accidentally destroyed before restand- 

 ardization was made and therefore the readings for it are not comparable 

 in actual amount to the brown cup nor to any other readings in the other 

 experiments. The equivalent for the brown cup was 178 sq. cm. of free 



10 11 12 



Fig. 14. Graphs for relative transpiration of four potted plants, 

 brown atmometer being used for evaporation rate. Exp. IX. 



water surface. The situation was in the open with exposure to sun and wind. 

 A heavy wind threw sand on the pots and thus spoiled the readings after 

 l'*38'"p.m. The atmometer readings for 2^ 47"" p.m. show that the maxi- 

 mum evaporation for the day was between 12 noon and I'* .30 p. m. Air 

 movement was confined to a very gentle breeze during the period covering 

 the readings. 



*Livingston, B. E., A radio-atmometer for measuring lisht intensities. Plant World, 

 XIV, pp. 90-99, 1911. 



