METHOD FOE PLANTS HAVING NO DEFINITE WILTING POINT. 51 



adjustment is then effected by means of the threaded nut on the 

 counterweight. 



When a fleshy plant with a well-developed root system is used, 

 and the soil contains a suitable amount of water, the system acts 

 essentially as described above. The plant will continually tend to 

 move downward from its initial position of equilibrium, owing to 

 the movement of water from the opposite side of the system to 

 replace the water transpired by the plant. As the soil becomes 

 drier this movement becomes less 

 marked and indeterminate, until 

 finally the direction of motion is 

 reversed, the plant moving up- 

 ward as its own weight begins to 

 be reduced through the loss of 

 water. 



This is well illustrated by the 

 observations given in Table XV, 

 showing clearly the three stages 

 characteristic of a balanced sys- 

 tem of this kind. The table includes observations made with a bal- 

 anced cactus plant {Opuntia ficus indica) and with a young lemon 

 plant {Citrus limonum), the latter serving to show the wilting of the 

 plant which accompanies the change in the direction of motion of the 

 system. 



Fig. 6.— A convenient counterpoise weight for use in 

 adjusting the balancing system. A coarse adjust- 

 ment is effected by moving the counterpoise 

 weight along the rod and clamping with a set 

 screw . A fine ad j ustment is then made b y means 

 of the threaded nut. 



Table XV. — Observations with two balanced systems, one containing a cactus plant and 



the other a lemon plant. 



Plant and time of observation. 



Weight. 



Notes. 



Cactus plant (Opuntia ficus indica): 



Feb. 8, 5.45 p. m 



Feb. 9, 9.30 a. m 



Feb. 11, 5 p. m 



Feb. 13, 5 p. m 



Feb. 14, 10 a. m 



Feb. 15, 10 a. m 



Feb. 16, 9.30 a. m 



Feb. 16, 5 p. m 



Feb. 17, 5 p. m 



Feb. 18, 5 p. m 



Feb. 20, 5 p. m 



Lemon plant (Citrus limonum): 



Dec. 5, 5 p. m 



Dec. 6, 5 p. m 



Dec. 7, 5 p. m 



Dec. 8', 5 p. m 



Dec. 9, 5 p. m 



Dec. 10, 5p.m 



Dec. 12, 5 p. m 



Dec. 13, 4 p. m 



Dec. 15, 4 p. m 



Dec. 17, 4 p. m 



Dec. 19, 5 p.m. 



Dec. 20, 5 p. m 



Dec. 21, 5 p. m 



Dec. 22, 5 p. m 



Dec. 23, 4 p. m 



230 



Grams. 



648.4 



648.1 



646.1 



644.8 



644.6 



644.4 



644.3 



643.9 



643.7 



643. 55 



642.85 



579. 41 

 574. 50 

 573. 55 

 570. 85 

 568.20 

 565. 83 

 559. 85 

 557. 75 

 553.40 

 549. 54 

 545. 77 

 544. 16 

 542.56 

 541. 95 

 539. 50 



Balanced and adjusted to zero. 

 Plant down; readjusted to zero. 



Do. 



Do. 



Do. 



Do. 



Do. 

 Balanced, no change. 



Do. 

 Plant up; readjusted to zero. 



Do. 



Adjusted to zero (Citrus limonum). 

 Plant down; readjusted to zero. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 

 Balanced. 



Plant up; readjusted to zero. 

 Plant up; wilting. 

 Plant up; wilted. 

 Plant up; lower leaves drying. 



