54 THE WATER-BALANCE OF SUCCULENT PLANTS. 



The plant had partly recovered from the blanching effects, but was much 

 shrunken, having- lost over 54 per cent of its original weight in the 18 

 months during which it had been cut off from a supply of water. It was 

 taken to be still capable of growth and of accumulating a water-balance if 

 a supply were furnished. 



ECHINOCACTUS No. 3. 



On March 6, 1908, a small Echinocadus from the bajada west of Tuma- 

 moc Hill was taken up, the smaller roots cut off, and it was set up on a 

 small pile of rocks on a stone platform. Exposure to the sun and evapo- 

 rating action of the air combined to dry out the plant to such an extent 

 that the ridges were undulating, thin, and drawn closely together, and the 

 plant had taken on a reddish tinge on November 5. The weight at this 

 time was found to be 3.893 kg., which was probably about six or seven 

 tenths of the original weight. 



The plant was now placed under the same conditions as No. 1. 

 On December 7, 1908, 32 days later, a gain of 14 grams in weight had 

 been made. Every precaution was taken to eliminate error, and the only 

 explanation available is that the increase represented water-vapor taken 

 up hygroscopically by the spines and other dead tissues (see page 56). 

 An adjustment of the preparation was now made, by which it weighed 

 3.921 kg. 



On January 30, 1909, a loss of 43 grams had ensued in the preceding 54 

 days, the weight now being 3.878 kg. Although the stage of desiccation 

 of this plant was far in advance of that of No. 1, it showed a relatively 

 high daily rate of loss, which might be attributable either to its immaturity 

 or to loss of water from the spines . 



A number of young flower-buds were beginning to push out, but these 

 did not develop beyond the form of small buttons, when they dried out. 

 The plant was now set in a dish of water, from which about 100 c.c. was 

 absorbed in two days, with an apparent increase of 14 mm. in circumfer- 

 ence, as estimated from the measurements between two ribs. The total 

 increase of weight on February 5 had been but 14 grams and on the 12th 

 this had been reduced to 6.5 grams. 



A box of loam was now prepared, the roots set in this, and water fur- 

 nished in the ordinary manner. On May 21 the measurements showed that 

 no further decrease appreciable by measurement had taken place, the trans- 

 piration being balanced by absorption. Upon lifting from the soil a number 

 of roots 8 to 10 cm. long, amply furnished with root-hairs, were found. 

 The plant was replaced in the soil and set in a shaded room. 



On August 1, 1909, the plant had apparently regained its original vol- 

 ume, being turgid, with the ribs separated and of a healthy color. This 

 specimen had been separated from a water-supply for 11 months, exposed 

 to great evaporating action, and when set in a moist soil had developed a 



