424 Spalding . — On the Traumatropic 
Pfeffer, who in every possible way has encouraged and aided 
the investigation, both by personal attention and by means 
of the admirable facilities of the Botanical Institute of the 
University of Leipzig. 
General Account of Phenomena. 
If a radicle of Lupinus albns , or other suitable species, 
preferably when it has attained the length of two or three 
centimetres, is branded just back of the apex with some con- 
venient instrument, such as a hot glass rod, the tip begins, in 
the course of an hour or more, to bend away, so that in a few 
hours the lower part of the radicle is strongly convex on the 
injured side. With subsequent growth the curvature con- 
tinues, and within a day or two, in extreme cases, the tip may 
have described an entire circle, more or less. The same 
change of direction follows other modes of inflicting injury at 
the same point, such as cutting, cauterizing with nitrate of 
silver, and the use of still other destructive agents. 
The whole course of events gives the impression of a sensi- 
tive organ that has received an injury and is avoiding further 
danger from the same source by bending away. Provisionally 
the reaction just described will be referred to as traumatropic 
curvature to distinguish it from a different curvature that is 
plainly mechanical. The latter appears just at the place 
where the injury is inflicted, and is a short, almost sharp, 
bend, with the concavity on the injured side. This mechanical 
bend may be produced by injury to the growing part of the 
root anywhere from within a millimetre to several millimetres 
from the extremity ; the traumatropic curvature, on the other 
hand, follows only when the injury is close to the apex, within 
i*5 mm., or sometimes a little farther back, as in the case of 
larger roots. A common case is represented in Fig. 1 , in 
which the long traumatropic curvature, a , with the convexity 
on the injured side, is strongly contrasted with the short 
mechanical bend, x , which is always concave on that side. 
The root thus operated upon continues its growth, if the 
conditions are favourable, but the injured part shows more 
