ELECTRICAL AND MAGNETIC PROPERTIES OF THE CELL 45 



volts is used, and the quantity passing through the cell decreased by inter- 

 posing a long filament and surrounding it with water. 



SECTION 16. Chemical Changes connected with Streaming. 



Beyond the changes due to the accompanying aerobic or anaerobic 

 respiration, no special chemical changes seem to be connected with the 

 existence and maintenance of streaming. Czapek 1 states that in the apical 

 meristems of curving roots reducing substances appear to increase, while 

 the oxidases decrease. This is probably the result of increased katabolism, 

 but no changes of this kind seem to take place in cells in which secondary 

 streaming has been induced by stimulation, provided they are well 

 aerated. If, however, the cells are insufficiently aerated and kept in semi- 

 darkness, a slightly increased acidity of the sap (organic acids), or even 

 the appearance of substances which have the power of reducing alkaline 

 solutions of silver salts may result. The same phenomenon is, however, 

 shown by non-streaming cells, and hence it has no direct connexion with 

 streaming. 



SECTION 17. Electrical and Magnetic Properties of the Cell. 



Hitherto but little experimental work has been attempted in this 

 direction, and, in spite of its importance, it rests almost entirely on 

 theoretical and frequently incorrect assumptions. It is, for example, 

 essential to know whether or not the existence of streaming is connected 

 with the presence of electrical currents in the cell, as Velten suggests 2 . 



Reinke, however, states that freely suspended streaming cells retain 

 any position in which they may be placed in a magnetic field, and hence 

 concludes that no electrical currents circulate in them. Even were Reinke's 

 facts correct, his conclusions would not be a necessary consequence of them. 

 It is easy, for example, to arrange two similar solenoids with interlacing 

 coils and opposed currents so that they shall exhibit no external electro- 

 magnetic properties. Moreover, as we shall see later, the cellulose wall is 

 distinctly ', tho^lgh weakly, magnetic, and hence a pronounced directive action 

 is usually exercised upon elongated cells freely suspended in a magnetic field. 

 Indeed, from a physical point of view, it appeared highly improbable that 

 all plant-cells possessed exactly the same magnetic permeability as water, 

 as the absence of all directive action in a magnetic field (Reinke) would 

 indicate. Reinke suspended plant-cells in hanging drops of water, and used 

 as his electro- magnet a hollow bar 300 mm. long and 40 mm. diam., 

 covered by a 17 mm. thick coil of wire charged by four Bunsen cells. The 



1 Ber. d. D. Bot. Ges., 1897, Vol. xv, p. 516. 



2< Velten, Flora, 1873, p. 122. First put forward by Becqnerel, Ann. sci. nat., 1838, ii. s&r. 

 T. IX, p. 6?. 



