. Experimental morphology. Protoplasm; Growth. 410 EFFECT OF ELECTRICITY [Ch. XVI Brtjnchoest ('84, p. 209) found- that the radicles of seedlings of Brassica grow, under otherwise similar conditions, at a cur- rent intensity* of B to B, towards the kathode, and at a current intensity of 8 towards the anode (Fig. 116).. BRASSICA Fig, 116. — Effect of different strengths of electric current on the radicle of Brassiea. At the right: strength of current, S; all strongly negative and growing well. At the middle: strength of current, S; after a few hours negative at the apex bu
. Experimental morphology. Protoplasm; Growth. 410 EFFECT OF ELECTRICITY [Ch. XVI Brtjnchoest ('84, p. 209) found- that the radicles of seedlings of Brassica grow, under otherwise similar conditions, at a cur- rent intensity* of B to B, towards the kathode, and at a current intensity of 8 towards the anode (Fig. 116).. BRASSICA Fig, 116. — Effect of different strengths of electric current on the radicle of Brassiea. At the right: strength of current, S; all strongly negative and growing well. At the middle: strength of current, S; after a few hours negative at the apex but positive higher up. At the left: strength of current, S; all positive, weak, and dead. (From Brunchoest, '84.) If decapitation has occurred the kathode turning does not follow, whereas the anode turning does occur as in the intact root. A similar result having been obtained with seedlings of various species, the conclusion was drawn that "the positive galvanotropic curving is a simple chemico-pathological phenom- enon which has only a superficial analogy with the directive movements of roots, and therefore does not deserve the name galvanotropism " [electrotropism]. The cause of the positive turning effect, it has been sug- gested, lies in the fact that certain substances, perhaps hydrogen peroxide and ozone, produced in electrolysis act more injuriously upon the positive than upon the negative side. According to another explanation, offered by RiscHAWi ('85), the positive curvature is due to the kathophoric action *The current density (see Chapter VI, § 1) is calculated from the following- data : The amount of copper deposited in a voltameter was mg. to 35 mg. per hour during the course of experimentation. A current of one ampere intensity deposits gramme of copper per second or mg. per hour per milliampere. Thus the strength of current varied from to 30' milliamperes. The determination of the density requires a knowledge of the cross
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