(422) 
gradually disappear: this disappearance also proceeds from above 
down ward. 
Both phenomena point to the existence of a polarity in the regulation 
of the protoplasmic currents, of which the impulse proceeds in the 
direction from the organic top to the base. 
If this stream-bundle is interrupted by a large cross-wound the 
communication is restored round the end of the wound. Now, however, 
the currents above and below the wound behave quite differently : 
the bands which proceed from the stalk of the prolification remain 
on the whole unchanged until they have arrived near the wound; they 
then partly deviate transversely and bend round the end of the wound, 
after which they go in a straight line to the leaf-stalk. Another part 
often turns back with a bend, namely if the currents are strong. So 
above the wound there occurs as it were a thrust and often a 
reflection which are entirely absent below the wound. 
Also this difference in the course of the currents above and below 
the wound points to a polarity in the regulation of the protoplasmic 
currents, the impulse evidently here also proceeding from the top 
and being directed to the organic base. 
We must add here in the first place that the currents, running 
in a non-proliferous leaf, which assemble like a fan from the top 
and the edge of the leaf and all pass into the leat-stalk, behave in 
exactly the same manner, when interrupted, as the stream-bundle 
which proceeds from a prolification downward; only this latter is 
generally more powerful and so more suitable for experimenting. 
Secondly we must remember that everywhere in the leaf there 
exists a very complicated network of currents, stretching between 
the numerous (+ 800 per sq.mm.) eross-beams which join the two 
sides of the leaf; so there exists an almost straight, but little intensive 
connection between any arbitrary pair of points on the leaf; so when 
we speak here for simplicity’s sake of the generation of currents, we 
mean the strengthening or thickening of the currents in such a way 
that they become visible with the naked eye or with the eye-glass. 
Thirdly the protoplasm in all currents moves continually or alter- 
nately in both directions and this applies also to those which develop 
from above and to those which disappear from above. 
Thus far my previous investigations had led me. 
The renewed investigation was begun again with these experiments ; 
they gave entirely concordant results. 
As the experiments with cross-wounded leaves had shown that 
it is possible to deviate the large nutritive currents from their way 
and to cause them to assume a lateral direction, the question was 
