1900] MECHANISM OF ROOT CURVATURE 35 
convex side, goes on with its curving as rapidly as, or more 
rapidly than, the whole root would have done. The opposite 
half, the one that would have become concave in the whole root, 
may also curve more than at the time of splitting, but this curv- 
ing is not invariable. This half may remain stationary for some 
time, then begin to curve toward the cut face, and therefore 
toward the brand. This curving in, however, has been delayed 
by the branding and only Ig per cent. of these roots have both 
halves curved in at a time when 42.4 per cent. of the control 
roots have both halves curved in. In the time that 69.2 per 
cent. of the control roots show both halves curved in, 81.4 per 
cent. of those that were branded on outer side of both halves 
show the same condition. Obviously, then, branding increases 
the rapidity of the curving of the convex half of the root. The, 
other half of the root usually does not continue the curving 
away from the brand, but it is considerably delayed in curving 
in toward the cut face, which nearly always takes place sooner 
or later in both control and branded roots. These facts, on first 
thought, seem to indicate that only the convex side is active in 
producing the curve of the whole root. That does not follow, 
however, when it is remembered what the tensions of the root are 
previous to stimulation. The concave half of the root when 
separated will curve outward only when the stimulus has reversed 
the tensions on that side and put the cortex under negative ten- 
sion in relation to the axial cylinder. If the tension were origi- 
nally at the maximum for roots it could be considerably decreased 
onthe concave side, and yet that half of the root could curve toward 
the cut face when separated from the other half. The fact that 
the concave half of the root sometimes curves farther, after 
separation, in the direction of the curve of the whole root, shows 
undoubtedly that the tension is sometimes reversed. In the 
cases in which the separated concave half curves no farther out- 
ward, the delay in curving with the cut face concave indicates 
that the original tension on the concave side was decreased 
but not reversed by the stimulus. Further experiments will be 
offered on this point. 
