[37] "This view has been the subject of a considerable amount of controversy. Wiesner denies the localisation of geotropic sensitiveness. Czapek, on the other hand, supports Darwin's theory. Recently Picard has attacked the problem in a new way (and) concludes that not only the root tip but also the entire growing zone is capable of perceiving gravitational stimuli.... As both Picard's experimental method and his interpretation are open to criticism, the author has repeated his experiments with a more satisfactory apparatus. He finds that in _Vicia Faba_, _Phaseolus multeflorus_ and _Lupinus albus_, both apex and growing zone are geotropically sensitive, the former being by far the more sensitive of the two, and the curvature of the growing zone being without a doubt largely induced by secondary stimuli transmitted from the apical region. Charles Darwin's views were therefore in the main correct."--Haberlandt--_Ibid_, p. 748. The experiments which I have described on the geo-electric response of the root tip and of the growing region offer convincing proof of the perception of the stimulus at the tip, and the transmission of the effect of indirect stimulus to the growing region. These experiments exhibit in an identical _uninjured_ organ: the excitatory reaction at the upper side of the tip, the cessation of excitation, and the excitation of the opposite side of the tip, following the rotation of the organ through +90°, 0° and -90°. The effect at the growing zone is precisely the opposite to that at the tip, _i.e._, an expansive reaction which results from the effect of indirect stimulus, in contrast to the contractile reaction due to direct stimulation. We may now proceed a step further and try to obtain some idea of the difference in the mechanics of geotropic stimulation of the shoot and of the root, to account for the different responses in the two organs. The reason of this difference lies in the fact that in the shoot the perceptive and responding region is one and the same; every cut-piece of stem exhibits the characteristic geotropic curvature. In the root the case is different; for the removal of the sensitive root-tip reduces or abolishes the geotropic action; the region of maximum geotropic perception is thus separated from that of response. It must be borne in mind _that this holds good only in the case of gravitational stimulus_, for the decapitated root still continues to respond to other forms of stimulation such as chemical or photic.