38 BOTANICAL GAZETTE [ JANUARY 
It might be supposed that there was a contradiction between 
the results of table XI and those of former tables. Here we find 
the concave cortex showing a stronger tendency to curve than 
the convex cortex, but in the former tables we found that on split- 
ting curving roots into two equal parts only the convex half con- 
tinued the curvature away from the branded side, while the con- 
cave half usually remained stationary for a time and then curved 
in toward the cut face and toward the branded side. This, how- 
ever, is easily understood through the tissue tensions. Since the 
cortex with ordinary growth tends to lengthen much faster than 
the axial cylinder, the cortex of the concave side might lose 
much of its positive tension and still be longer than the axial 
cylinder. The decreased tension on the concave side would 
allow the tension of the convex side to curve the whole root, even 
if the tension on the convex side did not increase. But if, under 
these circumstances, the root was split into halves, the concave 
half would stop curving, and if the tension on the concave side 
had not been neutralized or reversed, this half could even reverse 
its curve; that is, curve in toward the cut face. 
Table XI alone might seem to show that the concave side 
was the more active in producing the curve. We could not 
escape this conclusion if the curve were produced by the aggre- 
gate of the tendency of each individual tissue to curve. But 
recalling what we know of previously existing tissue tensions, 
we find it in complete harmony with the conclusion previously 
arrived at, that the stimulus diminishes tension on the concave 
side, and increases it on the convex side. Table XI especially 
confirms.the view that the tension on the concave side is dimin- 
ished, as well as changed otherwise. 
It is possible, however, that the cortex of straight uninjured 
roots has a tendency to curve more or less regularly one way of 
another. Table XII will show that this is not the case. 
This table is designed as control for XI. The roots were 
not branded, and were sliced in the same way as those in table 
XI. Since there was no curve the plane in which the three 
strips lie was not constant in relation to the seedling. In 
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