74 NUTRITION IN VEGETABLES, 
two fluids of different densities are separated from each 0 
by a membrane, the less dense is attracted by the denser. _ 
259. This phenomenon he has been inclined to refer 
galvanic action, which hypothesis he conceives to be mail 
supported by the following fact:—An empty bladder 
placed in a vessel of water, with the negative pole of a 
vanic battery in it, while the positive pole is on the out 
or in the water ; a current of fluid is then established inwal 
towards the bladder. As, then, the fluids of plants 
greater density than the external watery solutions, their ¢ 
trical action will correspond to that of the negative p 
and, accordingly, the fluids from without will be atti 
inwards. 
260. It is probable that there may be some electro-galv 
attraction exerted by fluids of different densities; this 
of inquiry has been only recently disclosed, and we can 0 
at present, allude to the probability of its leading to s 
explanation of the movement of fluids. We may ob 
that some late physiologists have been inclined to’ 
an inherent power of movement to the animal fluids, 
cially the blood: and, if this hypothesis be admitted, 
_ might be, perhaps, transferred to the explanation of 
motion of the fluids in plants, without venturing too far in 
problematical theories. The singular movement in the cel 
described by Corti and Amici, would naturally — “ 
under this explanation. 
261. The theory has been proposed by Saussure, that ' 
vessels of plants possess a contractile power analogous 
the peristaltic movement of the intestines; but there is 2 
proof of this property of the vessels. Decandolle, who de 
nies in toto the property of the vessels now stated, pi 
the theory, that as the movement takes place principally 
not solely by the cells, they are endowed with a contra 
mal heart, and, in this manner, by the alternate cor 
oS eae coe IS 
; upwards, 
