382 



MODIFIED CIKCUMNUTATION. 



CHAP. VIL 



do not fully apply to the small leaf here figured. The pinme 

 move forwards and at the same time sink downwards, whilst 

 the main petiole rises considerably. With respect to the degree 

 of movement : the two terminal pinnae of one specimen formed 

 together an angle of 100 during the day, and at night of only 

 88, so each had moved 31 forwards. The penultimate pinnae 

 during the day formed together an angle of 180, that is, they 

 stood in a straight line opposite one another, and at night each 

 had moved 65 forwards. The basal pair of pinnae were directed. 



Fig. 160. 



Acacia Farnesiana; A, leaf during the day; B, the same leaf at night. 



during the day, each about 21 backwards, and at night 38 

 forwards, so each had moved 59 forwards. But the pinnso at 

 the same time sink greatly, and sometimes hang almost perpen- 

 dicularly downwards. The main petiole, on the other hand, 

 rises much : by 8.30 P.M. one stood 34 higher than at noon, 

 and by 6.40 A.M. on the following morning it was still higher 

 by 10; shortly after this hour the diurnal sinking move- 

 ment commenced. The course of a nearly full-grown leaf was 

 traced during 14 h. ; it was strongly zigzag, and apparently 



