On the Artificial Production of Rhythm in 
Plants >. 
BY 
FRANCIS DARWIN and DOROTHEA F. M. PERTZ. 
T HE instrument used for the observations here recorded 
is a modification of the klinostat, which we have 
named the intermittent klinostat. 
In the ordinary instrument the plant is kept slowly rotating 
with the object of freeing it from geotropic and heliotropic 
curvatures. It is possible to imagine the action of the 
klinostat as being one of two distinct kinds. We may 
suppose that either the plant is not influenced by the stimulus 
because it is never long enough in one position, or that 
it is influenced by the stimulus the whole time, and does 
not curve because it is equally stimulated on ail sides. 
In a research c On the circumnutation of unicellular organs V 
one of us observed Phycomyces on a vertical klinostat, and 
found that it exhibited a movement simulating circumnuta- 
tion, but which was reversible by reversing the driving gear. 
It was clear that this movement was the result of heliotropic 
stimulation causing a regular series of slight curvatures by 
1 A short paper on this subject was read by us at the Cardiff meeting of the 
British Association, 1891. 
2 F. Darwin, Bot. Zeitung, 1881, p. 473. 
[Annals of Botany, Vol. VI. No. XXIII. October, 1892.] 
