272 Cc. U. ARIENS KAPPERS 
salt, was influenced by a constant current, the movement was 
in the direction of the kathode, but that this direction of gal- 
vano-taxis may be reversed by placing the animal in a stronger 
(even physiological) solution of salt. If in the latter case the 
constant current was transmitted through it, a movement 
towards the anode was observable. This phenomenon of re- 
versal, first observed in a galvano-tactic process, was confirmed 
shortly after in a galvano-tropic process, in the case of the root- 
tips of pease. 
Gassner’ found that an increase of salt in the medium influ- 
ences the effect of the constant current in those objects also. 
When he increased the quantity of salt of the water in which 
pea-roots sprouted, the constant current could no longer cause a 
kathodic tropism. He was inclined to ascribe this to a dim- 
inution in the quantity of electricity running through the tip 
of the root, since the greater conductivity of the water (salt 
solution) caused a greater quantity of electricity running through 
the solution itself. 
Schellenberg?* obtained the same result, but went even far- 
ther, and on increasing still more the percentage of salt was 
able to obtain a reversed tropism, the root then growing to th 
anode. 
If the percentage of KCl in the water was only 0.074 per cent 
the root-tip continued to grow kathodie galvano-tropic; if, 
however, the percentage was raised to 1 per cent, a distinct 
anodic direction in the growth appeared, and with a fair de- 
gree of exactness such a concentration of KCl could be found in 
which, after the transmission of the constant current, no trop- 
ism was evinced." 
* Gassner. Der galvano-tropismus der Wurzeln. Botanische Zeitung, 1906, 
Parts 9-11. 
23 Schellenberg. Untersuchungen iiber den Einfluss der Salze auf die Wach- 
stumsrichtung der Wurzeln, zunichst an der Erbsen Wurzel. Flora, vol. 96, 
1906, p. 474. 
“Tt may be mentioned that the current strength which caused this tropism 
was but slight, and varied from 1/10 to 1/1000 milliampere, with a density of 
current of 0.0025 to 0.000025 milliampere per sq. em. 
That Elving’s curves (which are also anodic) could be formed under these 
circumstances is out of the question, since Brunchorst found the current density 
necessary in this case to be about 0.2 milliampere. 
