422 Vines . — On Epinasty and Hyponasty . 
before and after being kept in darkness is shown in the ac- 
companying figures. 
The curvature in question is not due to flaccidity of the 
tissues, for the leaves are fully turgid after their sojourn in 
darkness, and when an attempt is made to lift them up into 
the horizontal position they spring back into the recurved 
Fig. 7. Normal plant of Heli- 
anthus annuus. 
Fig. 8. Same plant after twenty- 
four hours in darkness. 
position with considerable force. Moreover, the leaves show 
the same curvature, and in the same time, when (a) the plant 
is rotated on the clinostat in darkness, and (b) when the plant 
is placed upside down in darkness. 
On being again exposed to light, the recurved leaves regain 
the horizontal light-position within twenty-four hours. 
Precisely similar results were obtained on repeating these 
