Curvature of Roots. 431 
had grown in twenty-four hours quite rapidly, the increase 
in length ranging from 2 to 8 mm. 
10. Eleven aerial roots of Vitis gongylodes were branded 
in the usual way at 10 a.m. At 3.30 p.m. all showed plain 
deflection, one being curved at nearly a right angle. The 
next day the traumatropic curvature was more pronounced, 
as was also the short mechanical bend at the point of 
branding. 
A longitudinal section shows that the root-cap in this 
species is inconspicuous, its entire length from the extremity 
to where it is continuous with the epidermis being 0*5 mm. or 
less. As in the case of Anthurium , the traumatropic curva- 
ture lies so far back of the extremely small root-cap that the 
mechanical action of the latter is not to be thought of as its 
cause. 
11. Two roots of Anthurium sp. were wounded as a result 
of their growing against the sharp point of a pin previously 
fixed obliquely in their path. Five hours after the pins had 
been placed in position the roots were examined and both 
were beginning to turn away. One had already been pene- 
trated by the pin to a depth of approximately 2 mm. After 
twenty-three hours this one was still more strongly deflected, 
the other not having continued to curve much farther from 
its path. Deflection was also observed to take place as the 
result of merely pricking the growing-point with a clean 
needle, which was immediately withdrawn after making the 
wound. 
Extent and Direction of Wound. 
While the experimental work was in progress it soon 
became evident that the nature, direction, and extent of the 
wound constitute an important factor that had received too 
little attention. Accordingly an attempt was made to observe 
and compare with some degree of precision the results of 
wounding by cutting in different ways. 
If the tip of a root is cut off square across, it does not 
exhibit traumatropic curvature, but if cut obliquely it becomes 
