F" 



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J*' 



SPIRAL TWIKEES. S 



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stick, and was steadily revolving. I then took a longer stick and 

 tied up the shoot, so that only a very young internode, 1| of aii 

 inch in length, was left free ; this was so nearly uj^right that its 

 L revolution could not he easily ohserved ; hut it certainly moved, 



and the side of the internode which was at one time convex be- 

 came concave, which, as we shall hereafter see, is a sure sign of 

 the revolving movement. I will assume that it made at least one 

 revolution during the first twenty-four hours. Early the next 

 morning its position was marked, and it made the second revolu- 

 tion in 9 h. ; during the latter part of this revolution it moved much 

 quicker, and the third circle was performed in the evening in a 

 little over 3h. As on the succeeding morning I found that the 

 shoot revolved in 2h. 45 m., it must have made during the night 

 four revolutions, each at the average rate of a little over 3 h. I 

 should add that the temperature of the room varied only a little. 

 The shoot had now grown 3^ inches in length, and carried at its 

 extremity a young internode 1 inch in length, which showed slight 

 changes in its curvature. The next or ninth revolution was 

 effected in 2 h. 30 m. From this time forward, the revolutions were 

 easily ohserved. The thirty-sixth revolution was performed at 

 the usual rate ; so was the last or thirty- seventh, but it was not 

 quite completed ; for the internode abruptly became upright, and, 

 after moving to the centre, remained motionless. I tied a weight 

 to its upper end, so as to slightly bow it, and thus to detect any 

 movement ; but there was none. Some time before the last revo- 

 lution the lower part of the internode had ceased to move. 



A few more remarks will complete all that need be said on this 

 one internode. It moved during five days; but the more rapid 

 movement after the third revolution lasted during three days and 

 twenty hours. The regular revolutions, from the ninth to thirty-^ 

 sixth inclusive, were performed at the average rate of 2 h. 31m. : the 

 weather was cold ; and this aifected the temperature of the room^ 



especially during the night, and consequently retarded a little 

 the rate of movement. There was only one irregular movement, 

 when a segment of a circle was rapidly performed (not counted in 

 the above enumeration) ; and this occurred after an unusually slow 

 revolution of 2 h. 49 m. After the seventeenth revolution the inter- 

 node had grown from 1^ to G inches in length, and carried an inter-i 

 node li inch long, which was just perceptibly moving; and this 

 carried a verj^ minute ultimate internode. After the twenty-firat 

 revolution, the penultimate internode was 2| inches long, and 

 probably revolved in a period of about three hours. At the: 



b2 



