38 THE EXPERIMENTAL INDUCTION OF DEPENDENT NUTRITION. 



the movement was continued so that a total arc of 180° had been com- 

 pleted by 10 a. m. on the 19th, at which time the terminal portion was 

 in a horizontal position, directed away from the window, the total sweep 

 occupying- about 47 or 48 hours, perhaps less. The reverse which would 

 carry the tip toward the light began immediately, the tip having risen 1 cm. 

 by 3" 20" p. m., and reached the horizontal position with tip toward the 

 window at 2 p. m. on the 20th. 



The complete cycle was thus completed in something over 60 hours, the 

 movement away from the window consuming twice as much time as that 

 toward the window. On the next cycle the minor movement at a position 

 near the midway was not noted accurately, but it was not unduly prolonged, 

 for the extreme position with the tip away from the window was reached 

 in 2 days as before. At 7 a. m. on the 23d the tip had retracted 15 mm. 

 from this position, becoming erect by noon, and was found in a horizontal 

 position at 10 o'clock the next morning. The next movement was not 

 observed, but on May 29 it was again noted at the median position, and the 

 minor movement was prolonged so that it had departed from this 4 cm. 

 on the 30th and was found in the extreme position with tip away from 

 the window on the 31st. At 2 p. m. the movement toward the window had 

 raised the tip 3 cm., and this phase of the nutation was completed within 

 the day. (Plate 8.) 



The movement was now carried out with greater irregularity, which may 

 be ascribed to the rising temperatures. Although the extreme position 

 was reached occasionally, yet the shoot would be held in the median posi- 

 tion for several days, in which it made movements of small amplitude. 

 On July 30 it was noted that no movement of any consequence was to be 

 seen during- this and the day previous. 



On October 5, 1909, the preparation was again brought under observa- 

 tion and it was found that the shoot was moving- somewhat irregularly 

 through an arc the chord of which would measure about 9 cm. The tem- 

 peratures were now much lower than midsummer, the shaded laboratory 

 probably not rising above 85° F. 



On October 15, 1909, the stem was moving through an arc the chord 

 of which would measure about 5 or 6 cm., with greater irregularity and 

 shorter cycle than before, the complete movement not occupying more 

 than 2 days. Movements of a second etiolated shoot were observed in May, 

 but were of small amplitude. In October, however, 3 etiolated shoots, 

 in addition to the principal one described above, were found to be in 

 motion, and the tips were seen to change position as much as 3 or 4 cm. 

 in cycles of varying lengrth. 



The analysis of the curvatures by which the movements were produced 

 showed that the entire etiolated shoot was affected. If the movement from 

 the extreme position toward the window be followed, the following pro- 

 cedure would be noted: A concavity on the upper side of the stem would 



