CHAP I. GOSSYPIUM. 23 



The angles above the horizon at which the cotyledons of another 

 seedling stood at different hours is recorded in the following 

 short table : 



Oct. 20 2.50 P.M. 

 4.20 

 5.20 

 10.40 



Oct. 21 8.40 A.M. 

 11.15 

 9.11 P.M. 



25 abore horizon. 

 22 



35 



10 below horizo 



The position of the two cotyledons was roughly sketched at 

 various hours with the same general result. 



In the following summer, the hypocotyl of a fourth seedling 

 was secured to a little stick, and a glass filament with triangles 

 of paper having been fixed to one of the cotyledons, its move- 

 ments were traced on a vertical glass under a double skylight in 

 the house. The first dot was made at 4.20 P.M. June 20th ; and 

 the cotyledon fell till 10.15 P.M. in a nearly straight line. Just 

 past midnight it was found a little lower and somewhat to one 

 side. By the early morning, at 3.45 A.M., it had risen greatly, 

 but by 6.20 A.M. had fallen a little. During the whole of this 

 day (21st) it fell in a slightly zigzag line, but its normal course 

 was disturbed by the want of sufficient illumination, for during 

 the night it rose only a little, and travelled irregularly during 

 the whole of the following day and night of June 22nd. The 

 ascending and descending lines traced during the three days 

 did not coincide, so that the movement was one of circumnuta- 

 tion. This seedling was then taken back to the hot-house, and 

 after five days was inspected at 10 P.M., when the cotyledons 

 were found hanging so nearly vertically down, that they might 

 justly be said to have been asleep. On the following morning 

 they had resumed their usual horizontal position. 



Oxalis rosea (Oxalidese). The hypocotyl was secured to a little 

 stick, and an extremely thin glass filament, with two triangles of 

 paper, was attached to one of the cotyledons, which was '15 irch 

 in length. In this and the following species the end of the 

 petiole, where united to the blade, is developed into a pulvinus. 

 The apex of the cotyledon stood only 5 inches from the vertical 

 glass, so that its movement was not greatly exaggerated as long 

 as it remained nearly horizontal ; but in the course of the day it 

 both rose considerably above and fell beneath a horizontal posi- 

 tion, and then of course the movement was much exaggerated. 



