— 133 — 



The Sorghums were fixed by the lower part of the hypocotyl 

 in a vertical position, the apex being- upwards, and after being 

 injured in various ways on one side of the cotyledon, they were 

 kept at a suitable temperature for 21—23 hours in damp air in the 

 dari<, when they were examined. 



In those described as 'cut", two or three minute incisions 

 were made on one side of the cotyledon: the "burnt-' ones were 

 touched with a hot needle in a few places: "oiled" means that 

 one side of the cotyledon was painted with olive oil thickened 

 with animal charcoal, a method which is not very satisfactory owing 

 to the spreading of the oil, in spite of which the results are con- 

 sistent. 



Table II/ 



There can therefore be no doubt that injuring the cotyledon 

 tends to produce curvature towards the injured side. This may 

 remind us of the traumatic curves in roots described in The 

 Power of Movement in Plauts') as due to injury to one 

 side of the tip, but in the case of roots the curvature is from the 

 injured side. 



A few experiments were made to test the combination of the 

 traumatic effect with geotropism. 



The cotyledons of thirty-seven seedling Sorghums were oiled 

 on one side, nineteen of these were placed horizontally with 

 the injured side of the cotyledon upwards, the remainder horizontally 

 with the injured side below. In both cases the seedlings were 

 supported by the base of the hypocotyl, not, as in so many of our 

 experiments, by the cotyledon. After 22—23 hours the following 

 results were obtained. Of nineteen with the injured side upwards 

 all curved upwards (average angle 53°i. Of eighteen with the injured 



') P. 132. The curvatures were at the time believed to be due to contact- 

 stimulus. 



