a26 MODIFIED CIECUMNDTATION. 



Fig. 128. 



Chap. VH, 



SbonA^h 



7'dJ'a.m.S. 



Oxalis acetosella: circumnutation and 

 nyctitropic movements of ii nearly 



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 Pfeffer 

 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 affl'^ed 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 10.4.0 

 P.M., as shown in the fol- 

 lowing diagram (Kg. 129). 

 We here see that the leaflet 

 moved a little from side to 



full-grown leaf, with filament at 



tached to the midrib of one of the gijje^ ^S well as a little up 

 leaflets; traced on vertical glass dur- 

 ing 20 h. 45 m. 



and down, whilst asleep. 



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

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



