Nomenclature and Method. 
231 
ment known as the intermittent klinostat 1 has been used with 
advantage in certain researches. We first used it to determine 
a small point in regard to rectipetality. This term (which has been 
replaced to some extent by autotropism ) was designed by Vochting 
to describe the fact that a tropically curved organ becomes straight 
on the klinostat. It was assumed that the plant is freed from 
external stimulus and that therefore the effect is due to an internal 
regulating power. But if in the case of the continuous klinostat, 
the stimulus of gravity is only distributed (Theory ii.) the straight¬ 
ening may be the result of symmetrical stimulation of an organ 
in an asymmetrical condition induced by geotropic curvature. This 
can be avoided by means of the intermittent klinostat which 
rotates through 180° at regular intervals. A shoot curved geo- 
tropically is fixed to the intermittent klinostat so that the plane of 
curvature is horizontal. “ The succession of half turns prevents 
any geotropic distortion in the plane at right angles to the original 
plane of curvature, while in that plane the plant is free to increase 
or diminish its curvature apart from any fresh gravitation- 
stimulus 2 3 .” Under these circumstances rectipetality occurs just 
as it does on the continuous klinostat. The interest of the 
experiment is that so far as the original plane of curvature is con¬ 
cerned the plant is truly removed from the effect of gravitation. It 
may therefore be said that in this respect the intermittent 
klinostat acts on a principle distinct from that of the continuous 
instrument in which the stimulus is distributed. 
The intermittent klinostat may also be used to observe the 
effect of opposing stimuli; thus if a straight shoot is fixed 
to the intermittent klinostat it is subjected to prolonged alternate 
stimuli and falls into the curious rhythmic condition described 
by Miss Pertz and myself. 5 In the next lecture we shall see how 
successfully Fitting 4 employs both forms of instrument. 
1 D. F. Pertz and F. Darwin, Proc. Cambridge Phil. Soc., Vol. 
VII., 1891, also Annals of Botany, 1892. 
2 D. F. Pertz and F. Darwin, loc. cit. 
3 Annals of Botany, 1892. 
4 Pringsheim’s Jahrb, 1905. 
