Spalding : Mechanical adjustment of suaharo 



61 



The first observations on this plant were made some three 

 months after the opening of the laboratory, and judging from its 

 full appearance and from other experiments, it is probable that the 

 first effect of the water had been to cause an expansion of the stem. 

 By the time observations were begun this had entirely ceased, 

 but, as will be seen, it is evident that the presence of water in the 



soil was still exerting an influence. 



January 9 to February 



6, while the furrows of number i contracted ■^-^, g^^ and ^^^ of an 

 inch, two furrows of number 2 contracted only -V and a third ^ 



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The difiference in the effect of the rain of Feb- 



ruary 6 was even more marked. While the furrows of number i 



January 



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Figure 2. Curves for suaharo number 2. The measurements from which the 

 three lower curves were derived were made on comparatively young branches, those 

 for the two upper on lower and older parts of the stem. Rain, February 6 (0.54 in.). 



showed an increase of H to |J of an inch, those of number 2 

 only increased -^^ to ^^ of an inch, indicating that previous to the 

 rain the cells of number 2 were much nearer their limit of expan- 

 sion than those of number i. It is evident then that the plant 

 was able to avail itself to a considerable extent of the waste water 

 of the laboratory, notwithstanding the large quantity of alkaline 

 salts and other chemicals carried by it ; and this is farther shown 

 by its behavior after the period of expansion had ceased. Up to 

 March 26, when the other cacti had been contracting for over 



