62 THE WATER-BALANCE OF SUCCULENT PLANTS. 



On December 8, 1908, the weight of the preparation was found to be 

 15.940 kg., indicative of a loss of 1.130 kg. in 31 days, or a rate of 36.4 

 grams daily. 



On May 12, 1909, two fruits had been lost and a new base provided 

 which weighed 1.640 kg. The total weight was now 11.370 kg., with a 

 total actual loss of 4.840 kg., at the rate of 38 grams daily for the entire 

 period of six months. 



The excessive rates displayed by this plant in comparison with Nos. 7 

 and 8 in the inclosed room are doubtless due to exposure to the evaporat- 

 ing effects of sunlight and wind, and are, of course, much greater than 

 that of No. 1. 



The plant was now set in the soil near the east end of the parapet of 

 the laboratory, and on August 1, 1909, had regained all of its original 

 plumpness. It is to be noted that before being put in the soil it had lost 

 about 35 per cent of its original weight, or about 40 per cent of its entire 

 supply of water. 



Intervals were marked around the circumference on January 6, 1909, 

 and these were measured frequently until May. At first some of those on 

 the northern side, where the ridges were most widely separated, began to 

 increase their separation, but a total contraction ensued by which the cir- 

 cumference had diminished 13 cm. by May 21, 1909, an amount six times 

 as great as that of No. 6, in the inclosed room, which had undergone pre- 

 vious desiccation. The data also show that a loss in weight over six 

 times as great had also ensued. The total contraction on the north side 

 of the plant among the more widely separated ridges was 145, as com- 

 pared with 213 on the southern exposed surface. 



On October 17, 1909, the apical spines had not been pushed apart, and 

 8 greenish fruits were still retained. The plant was now taken up and it 

 was found to have developed a great number of small roots , which spread 

 out in all horizontal directions from the base in a dense tangle. All were 

 broken off except a mass that might have been inclosed in a space of 100 

 cm . These roots and the soil particles that could not be shaken off might 

 fairly be taken to be equal in weight to the fruits that had been lost since 

 the plant was set out, so that the weight now, 20.370 kg., represents a 

 draft comparable to that obtained on the last weighing. It weighed 

 17.010 kg. when taken from the soil, November 5, 1908, and this had 

 decreased to 11.370 kg. in May, 1909, by deprivation of water-supply, and 

 after it had been replaced in the soil it had developed a root-system and 

 made a gain of 9.600 kg., which was a net gain of 3.360 kg. over its origi- 

 nal weight. Measurements by Mrs. E. S. Spalding showed that the circum- 

 ference of the upper part of the trunk had increased 33 cm. since May, 1909. 

 On October 20, 1909, the weight, after 3 days in the laboratory, was 

 21.155 kg. gross, 20.285 kg. net. The preparation was now placed on the 

 stone wall with No. 3. 



