CHAP. I. BRASSICA. 15 



'23rd to 6.45 A.M. on Dec. 25th. No doubt the natural move- 

 ment was much disturbed by the two legs having been tied 

 together ; but we see that it was distinctly zigzag, first in one 

 direction and then in an almost opposite one. After 3 P.M. on 

 the 24th the arched hypocotyl sometimes remained stationary 

 for a considerable time, and when moving, moved far slower than 

 before. Therefore, on the morning of the 25th, the glass fila- 

 ment was removed from the base of the basal leg, and was fixed 

 horizontally on the summit of the arch, which, from the legs 

 having been tied, had grown broad and almost flat. The 

 movement was now traced during 23 hours (Fig. 5), and we 



Fig. 5. 



Bmssica oleracea: circurnmtating movement of the crown of a buried and 

 arched hypocotyl, with the two legs tied together, traced on a hori- 

 zontal glass during 23 hours. Movement of the bead of the filament 

 magnified about 58 times, and here reduced to one-half original 

 scale. 



see that the course was still zigzag, which indicates a tendency 

 to circumnutation. The base of the basal leg by this time had 

 almost completely ceased to move. 



As soon as the cotyledons have been naturally dragged from 

 beneath the ground, and the hypocotyl has straightened itself 

 by growth along the inner or concave surface, there is nothing to 

 interfere with the free movements of the parts ; and the circum- 

 nutation now becomes much more regular and clearly displayed, 

 as shown in the following cases : A seedling was placed in 

 front and near a north-east window with a line joining the 

 2 



