405 
Bayliss. — On the Gcilvanotropism of Roots. 
of curvature was brought about by differences of current density or by 
passing the current for varying periods of time, keeping the density 
constant. 
Dr. Gassner does not appear in any of his experiments to have tried 
the method of applying the electrodes directly to the root and then by 
varying the points of application changing the direction of the current. 
His current always traversed the root horizontally ; and thus, by using 
only this one direction he has missed most of the evidence which in my 
experiments leads to a different interpretation of Galvanotropism. 
Moreover, although his work shows that the utmost care has been 
taken to avoid any source of error, the experiments were conducted without 
the use of a klinostat — a sufficiently obvious precaution wherever possible, 
in dealing with root curvatures : also with the exception of the experi- 
ments on root-tips, the roots were entirely immersed in water or gelatine — 
a condition under which they lack aeration in greater or less degree, and in 
consequence have a diminished power of response. 
It seems highly probable, then, that the curvatures obtained by 
Dr. Gassner were essentially traumatropic, and that, so far as they are 
concerned, the interpretation of them given in section 7 is a correct one. 
But it is a far cry from this to the assertion of the identity of Galvano- 
tropism with a special form of Traumatropism (‘ Auf Grund eingehender 
Untersuchungen und Vergleiche kam ich zu dem Ergebnis,dass der Galvano- 
tropismus auf Traumatropismus zurtickzufuhren ist ’). Galvanic currents 
can cause injury, in which case the resulting curvature is traumatropic. 
My own experiments, however, make it clear that galvanotropic curva- 
tures can be obtained without injury to the root. Similar curvatures can 
be produced by dissimilar causes ; in the one case of injury ; in the other as 
response to a stimulus which no more involves injury than does the shifting 
of ‘ statoliths * in response to a changed direction of geotropic action ; and 
that the term traumatropic could in no way be applied to these. 
Further, by constantly varying the direction of the current it was 
proved quite conclusively that the + or — direction of the curve depended 
on the position of the positive or negative electrodes : moreover, further 
experiments all pointed to the analogy of these curves with those produced 
by a chemotropic stimulus. 
Jan . , 1907.. 
J. S. B. 
