426 Spalding . — On the Traumatropic 
degree, less definite. Removal of some portion of the tissue 
by cutting, notwithstanding the practical difficulty of cutting 
exactly to a given depth and in a certain direction, has been 
satisfactorily employed. Alcohol was used for the purpose 
of ascertaining what might probably be attributed to its use 
in Darwin’s shellac mixture, but although its influence was 
strikingly manifest, it was found difficult to restrict its action 
to a known area and depth. Besides branding, the appli- 
cation of heat by bringing the tip of the root into contact 
with the side of a glass retort containing boiling water, and 
holding it there a certain number of seconds, gave interesting 
and definite results. 
Roots that had been operated upon were commonly allowed 
to grow in water of the temperature of the room in which the 
work was carried on. This was kept during the day at 
approximately i8° C., but of course varied considerably in 
the course of twenty-four hours. Other roots were grown in 
moist air, but in general the results were less prompt and 
certain than when they were grown in water. In both cases 
they were suspended so that the radicle pointed vertically 
downwards. In still other cases, in order to retain as perfectly 
as possible the normal conditions, they were removed from 
the sawdust in which they had grown only long enough to 
inflict the wound, and were then returned to it. 
In an extended set of experiments growth was suspended 
for a number of days, after previous wounding, by placing the 
radicles in plaster-casts in the manner described by Pfeffer h 
Growth was also suspended by keeping the radicles in water 
at a temperature of o° C. for some days, but the use of plaster- 
casts was found preferable. These latter experiments were 
varied by branding after removal from the casts. 
The klinostat was employed as far as was necessary to 
demonstrate, the independent, though contemporaneous, action 
of traumatropism and geotropism. 
1 Druck- und Arbeitsleistung, p. 6, et seq. 
