326 MODIFIED CIRCUMNUTATION. 



Fig. 128. 



CHAP. VII. 



Oxalis acetosella : circumnutation 

 nyc 



down in this and all other 

 cases. By 6.45 A.M. on the 

 following morning it had 

 risen considerably, and con- 

 tinued to rise for the next 

 hour; but, judging from 

 other observations, it would 

 soon have begun to fall again. 

 Between 11 A.M. and 5.30 P.M. 

 the leaflet moved at least four 

 times up and four times 

 down before the great noc- 

 turnal fall commenced; it 

 reached its highest point at 

 noon. Similar observations 

 were made on two other 

 leaflets, with nearly the same 

 results. Sachs and Pfeifer 

 have also described briefly * 

 the autonomous movements 

 of the leaves of this plant. 



On another occasion the 

 petiole of a leaf was secured 

 to a little stick close beneath 

 the leaflets, and a filament 

 tipped with a bead of sealing- 

 wax was affixed to the mid- 

 rib of one of them, and a 

 mark was placed close behind. 

 At 7 P.M., when the leaflets 

 were asleep, the filament de- 

 pended vertically down, and 

 the movements of the bead 

 were then traced till 10.40 

 P.M., as shown in the fol- 

 lowing diagram (Fig. 129). 

 We here see that the leaflet 

 moved a little from side to 



tropic movements of a nearly 

 full-grown leaf, with filament at- 

 tached to the midrib of one of the s i(J e as we n as a little up 

 leaflets; traced on vertical glass dur- d d ^^ 



ing 20 h. 4o m. 



* Sachs in 'Flora,' 1863, p. 470, &c.; Pfeffer, 'Die Period. Bewe- 

 gungen,' &c., 1875, p. 53. 



