36 BOTANICAL GAZETTE [JANUARY 
In comparing split roots, both halves of which have been 
branded on the outer side of the tip, with control roots that 
have likewise been split but not branded, a notable difference is 
seen after a few hours from the time of branding both in the 
localization and the amount of the curve. Fig. 1 shows this dif- 
ference, a being a half root that was not branded, and 4 one that a 
was branded on the outer side of tip. These curves 
were projected directly on paper, and show about 
the average condition ina set of sixteen roots, all 
of which were split throughout the length, with a 
cotyledon attached to each half root. The half A 
roots were paired with their original fellows, and 
eight roots had both halves branded on the outer sect 
side of the tip; eight were not branded. Six hours after splitting 
all the branded half roots except one are curved more than 90°, 
and the curve is localized in the region in which the traumatropic 
curvature takes place. Only five half roots out of sixteen not 
branded had curved as much as go°, and the curve extended over 
a longer zone of the root. In these roots there was no difference 
in the time after splitting at which the curving began. This is 
only one set out of a number which showed the same general 
result. This result shows conclusively that the stimulus increases 
the tissue tension on the convex side of roots in the zone in 
which the traumatropic curvature is produced. 
In the experiments shown in table XI roots were used that 
were already curved from branding, but in which the curve was 
still progressing, and in which, therefore, the conditions that 
bring about the curvature were still present. The roots were 
split at a time after branding which is indicated in the second 
column. The roots were sliced and split according to the method 
employed for table VII, and the three strips of convex cortex, 
axial cylinder, and concave cortex were observed with special 
attention to the curving of the parts after separation. The lettering 
is the same: x stands for the convex cortex, wv for the concave 
cortex, and a for the axial cylinder. Ina comparatively large 
number of cases both x and » pull away from a, x straightening 
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