ELECTRICAL AND ELECTRO-MAGNETIC THEORIES 109 



theoretically counterbalance and involve no external consumption of energy, 

 would not do so in practice, for the protoplast is far from being a perfect 

 machine, and indeed is in many respects further from perfection than 

 a steam-engine. 



K If cells of Trianea, Elodea^ Vallisneria^ &c., are placed in localized 

 contact with a drop of a fairly strong solution of methyl-violet or cyanin ! , 

 it can often be seen when streaming is very slow that the dye is carried with 

 the plasma and not in the opposite direction (Fig. 13). Hence we may 

 safely conclude that the protoplasm and the contained free water move 

 in the same direction. 



If the water were absorbed from and excreted into the cell-sap in such 

 a manner as to produce forward movement in the protoplasm, the cell-sap 

 would of necessity rotate in the opposite direction to the protoplasm, and 

 with greater velocity than it. Neither of these conditions, however, 

 ever occurs in plant-cells. An oblique external exudation of water is 

 impossible in the case of cuticularized hair-cells which exhibit streaming, 

 and as regards uncuticularized cells immersed in water, a simple calculation 

 shows that a cell of Nitella exhibiting active streaming would need to 

 absorb and excrete more than 2000 times its own volume of water in the 

 course of a day. Suspended particles in the immediate neighbourhood of 

 the cell exhibit no signs of any such exudation, which moreover the physical 

 properties of the cell-wall render impossible. 



It is also certain that the motion is not produced in a similar manner 

 to the phenomenon of thermo-diffusion, for the necessary difference of 

 temperature does not exist, and the other conditions are not fulfilled. 



There only remain to be discussed the electrical theories put forward 

 by Amici, Dutrochet, and Velten, and the surface-tension theory as 

 propounded by Berthold, none of which, however, affords a completely 

 satisfactory explanation. 



SECTION 50. Electrical and Electro -magnetic Theories of Streaming. 



Amici 2 concluded that the chloroplasts acted as Voltaic elements, 

 and electrically propelled the endoplasm. This theory was accepted by 

 Dutrochet and Becquerel, but is now no longer tenable, even although 

 Velten and Hermann (1. c.) still consider the chloroplastids to have an 

 independent power of movement of their own. One experiment performed 

 by Becquerel was to pass a current through a spiral wire arranged parallel 



1 Solutions which rapidly tinge the protoplasm must be used, although these shortly prove fatal. 

 Cf. Pfeffer, Unters. a. d. Bot. Inst. zu Tubingen, 1886, Bd. II, p. 201. 



2 Cf. Dutrochet, Ann. sci. nat., 1838, ii. ser., T. ix, p. 78; also Dutrochet and Becquerel, 1. c., 

 pp. 85-7. 



