THE MOLECULAR FORCES IN PLANTS. 135 



1 See Nowoczck in Haberlandt's Wissensch.-prakt. Unters. auf dem GeUete 

 d. Pftanzenbaues, Bd. 1, p. 122. 



2 See Schroder, Untersuchungen aus dem botan. Institut zu Tubingen, Bd. 2, 

 p. 18. 



3 See Detmer, Landivirthschaftl. Jahrbiiclter, Bd. 11, p. 230. 



54., The Action of Electricity on Plants. 



Comparatively little is as yet known concerning the action of 

 electricity on plants, especially as regards the finer details. 1 The 

 chief fact of physiological interest is that constant currents, as 

 also induction currents, are not without influence on the move- 

 ments of the protoplasm, since they usually retard or completely 

 arrest the movements, and ultimately cause the death of the cells. 



To study the phenomena in question, we employ young leaves 

 of Elodea, or hairs from the younger parts of a vegetable mar- 

 row. We mount the 

 objects in a drop of 

 water, on a slide of 

 the form indicated 

 in Fig. 45. On the 

 glass slip G are FlG . 4 5> _ object-glass for investigating the action of 

 Cemented by means electric currents on plant structures. 



of asphalte varnish (a solution of asphalte in oil of turpentine) 

 two brass plates, If, If, to each of which is soldered a binding 

 screw. The two strips of tinfoil, St, St, are attached to the 

 brass plates, and to the plate of glass, by means of asphalte 

 varnish. A space is left between them, and here is placed the 

 drop of water in which the object to be examined is mounted. 

 To study the influence of induction currents upon the plant cells, 

 we connect up the ends of the wires from the induction apparatus 

 by means of the binding screws, and can then make microscopical 

 observations while the currents are acting upon the cells. It is 

 important in physiological experiments to be able to regulate the 

 strength of the current, and for this purpose we employ an in- 

 duction apparatus such as is employed for medical purposes. The 

 apparatus is usually supplied in a suitable case, together with 

 the current-generating element. The regulation of the strength 

 of the current may be effected by means of du Bois Reymond's 

 sliding apparatus (see Fig. 46), in using which we connect up 

 the ends of the primary coil A with the current generator and 

 the Rheotome, while the secondary coil B is joined up with the 



