360 LOCOMOTORY AND PROTOPLASMIC MOVEMENTS 



SECTION 78. Galvanotaxis. 



Electrical currents of no greater strength than those which normally 

 circulate through plants do not influence streaming or locomotory move- 

 ments. Since, however, strong currents act injuriously or even fatally, ones 

 of moderate intensity might be expected to produce some physiological 

 effect, such as the galvanotropic reaction of many motile organisms. 

 Furthermore, a sudden increase or decrease in intensity, as on making or 

 breaking the current, acts as a shock-stimulus, like a blow or sudden 

 pressure. A single make or break shock is sufficient to stimulate the 

 pulvinus of Mimosa pudica, whereas a series of successive shocks are 

 required to produce a complete reaction in tendrils or in the leaflets of 

 Oxalis. Electrical shocks produce the same effect in the plasmodia of 

 Myxomycetes, and in cell-protoplasts, as do mechanical ones *. According 

 to the properties of the organism and the intensity, frequency, and character 

 of the stimulus, either an acceleration of retardation of movement, or 

 a slight change of shape, or pronounced deformation may ensue. Further- 

 more, either electrical or mechanical shocks may cause cilia to contract or 

 may decrease or accelerate their movement. 



Electrical stimuli are especially of value in that their intensity and 

 duration can be exactly measured, and in that they can be locally applied 2 . 

 Since, however, their action in plants is merely that of shock-stimuli, no 

 special detailed description of their mode of action is required 3 . Certain 

 peculiarities, as compared with mechanical stimuli, are due to the fact 

 that the action is strongly polar, and that local electrolytic actions due 

 to the separation, sorting, or interaction of ions, may arise at every 

 point where the current passes from one medium to a dissimilar one 4 . 

 The physical differences between the make and break shocks naturally 

 induce differences in their physiological action 5 . It is, however, possible 

 that induction-shocks may exercise some special electrical influence in 

 addition to their more mechanical action. 



1 This similarity has been recently pointed out by E. Roesele (Zeitschrift f. allgem. Physiologic, 

 1902, Bd. II, p. 162) and by Ewart (On the Physics and Physiology of Protoplasmic Streaming in 

 Plants, 1903, p. 88). For facts see Kiihne, Untersuch. ii. d. Protoplasma, 1864, 1874, 1894; 

 Engelmann, Handbuch d. Physiologic von Hermann, 1879, Bd. I, pp. 366, 403; Verworn, Psycho- 

 physiologische Protistenstudien, 1889, p. no; Allgem. Physiologic, 3. Aufl., 1901, p. 431 ; Klemm, 

 Jahrb. f. wiss. Bot., 1895, Bd. xxvui, p. 647 ; G. Hermann, Studien ii. d. Protoplasmastromung bei 

 d. Characeen, 1898, p. 60 ; and the literature quoted in these works. 



2 For methods see Nageli u. Schwendener, Mikroskop, 2. Aufl., 1877, p. 462 ; Zimmermann, 

 Mikroskop, 1895, p. 231; Roesele, I.e., p. 143. Also Biedermann, Elektrophysiologie, 1895; 

 L. Hermann, Physiolog. Practicum, 1898. 



3 [The existence of a power of galvanotropic response to constant currents in plants hardly 

 coincides with this assumption.] 



4 Cf. Ewart, I.e., pp. 95, 99, 123 ; Ewart and Bayliss, Proc. of Royal Society, Nov., 1905, p. 63. 



5 Cf. Verworn, Allgem. Physiologic, 3. Aufl., 1901, p. 431 ; Fr. Schenck, Pfliiger's Archiv f. 

 Physiologic, 1897, Bd. LXVI, pp. 257, &c. The action of make and break shocks is given here, 

 as well as their relation to Pfliiger's law, and the deviations from it. 



