VARIATIONS OF THE WATER-BALANCE. 57 



On May 13, 1910, the weig-ht was 650 grams, a loss of 14 grams in 22 

 days, a rate of 0.6 gram daily. 



The lessened supply present may be taken to account for the fact that 

 during- the 182 days ending May 21, 1909, the loss was 82 g-rams, at the 

 rate of 0.4 gxam daily, while during- the 125 days ending May 13, 1910, the 

 rate was less than 0.3 g-ram daily. Even in this desiccated condition, after 

 having- been deprived of water for 26 months, the rate of relative loss was 

 greater than that of the tubers of Ibervillea which had been recently taken 

 from the soil. 



ECHINOCACTUS No. 5. 



On March 6, 1908, a large plant was found on Tumamoc Hill which 

 had fallen prostrate, but which retained absorbent connection -with the 

 soil by one large root. It had lain in this position for nearly a year and 

 was apparently sound and normal. The roots were cut away and the plant 

 was placed in an upright position on a pedestal of loosely piled rocks, 

 being fully exposed to the sun and to the evaporating action of the air. 



On November 5, 1908, the plant was removed to the room with No. 1, 

 and found to weigh 19.99 kg. It was mounted so that the preparation 

 weighed 20.937 kg. 



On December 8, 1908, the weight was found to be 20.850 kg., indicating 

 that the net loss during the previous 33 days had been 87 grams. No. 1, 

 which had twice its weight, lost but 32 grams during the same period. 



The facts suggest that the plants brought in from the open air continued 

 to lose water at a rate only slightly decreased and much greater than 

 that of a plant which had been indoors for several months. 



On February 13, 1909, the root- system was taken away by a clean trans- 

 verse cut, and a cylindrical cavity bored directly upward in the central 

 woody cylinder. A clay bougie of the form used in the Li-vingston atmo- 

 meter was fitted into this tightly, the seal being made with plaster of Paris, 

 waterproofed on the outside with grafting-wax. A rubber stopper through 

 a 40 cm. glass tube was fitted to the clay cylinder and the whole system was 

 filled with water and the preparation was set upright, with the lower end 

 of the tube immersed in a dish of water. The preparation was completed 

 at 2 p. m. 



The amount of water taken up between February 16 and March 5, 1909, 

 is sho-wn in table 18. 



The rate now began to fall more or less steadily until April 10, when it 

 varied from 7 to 10 c.c. per day. The exposed tissues had begnan to 

 decay and gave off a fetid odor, as if from proteinaceous decomposition. 

 The weight of the preparation, allowing for the mounting, was about 

 19.840 kg., showing a total net loss of about 990 grams in 153 days, with 

 an absorption of nearly the same amount. The total transpiration had 

 therefore been at about three times the rate of No. 1, which showed a 

 weight about double that of this plant. 



