VARIATIONS OF THE WATER-BALANCE. 



61 



The above results are notable by reason of the fact that this plant dis- 

 played approximately the same rate of loss during corresponding- periods 

 ending in May, 1909 and 1910. This may be attributable to the compara- 

 tively small depletion which it had suffered, since less than 13 per cent of 

 the original balance had been lost. 



ECHINOCACTUS No. 8. 



On November 7, 1908, a h&dX^hy Echinocactus was taken up, the roots 

 trimmed away neatly, and found to weigh 28.811 kg. It was now put on 

 a mounting, the total preparation weighing 29.976 kg., 19 ripening fruits 

 being included. The entire preparation was placed in room with No. 1. 



On December 8, 1908, the weight was found to be 29.780 kg., indicative 

 of a loss of 196 grams in the 31 days ending with this date, or at a rate of 6 

 grams per day. This plant was found to display a transpiratory activity 

 fairly parallel to No. 1. 



Table 21 shows a number of records taken between January 2 and 

 August 1, 1909. 



Table 21. 



•Nearly. 



fBy adjustment of scale. 



^Adjustment of scale made. 



ECHINOCACTUS No. 9. 



On November 7, 1908, a sound Echinocactus growing near the Desert 

 Laboratory was taken up, the root- system trimmed, and the plant placed 

 on a base of wire-netting, the entire preparation weighing 17.339 kg., of 

 which the mounting was 261 grams. The crown bore 22 ripening fruits. 

 This plant and No. 10 were comparable with Nos.~7 and 8, the latter 

 being placed in the room with No. 1. Nos. 9 and 10 were placed on an 

 open porch on the south side of the laboratory, where the full effect of the 

 sun and of the evaporating action of the air would be received. It is 

 noted elsewhere that the ridges on the side of these plants exposed to 

 the sun are generally closer than those on the northern side, and these 

 preparations were oriented with respect to this feature. 



