Page:Darwin - On the movements and habits of climbing plants.djvu/4

 stick, and was steadily revolving. I then took a longer stick and tied up the shoot, so that only a very young internode, 1¾ of an inch in length, was left free; this was so nearly upright that its revolution could not he easily observed; but it certainly moved, and the side of the internode which was at one time convex became 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 revolution 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 3 h. As on the succeeding morning I found that the shoot revolved in 2 h. 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 3½ 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 observed. 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 revolution 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. 31 m.: the weather was cold; and this affected 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 internode had grown from 1¾ to 6 inches in length, and carried an internode 1⅞ inch long, which was just perceptibly moving; and this carried a very minute ultimate internode. After the twenty-first revolution, the penultimate internode was 2½ inches long, and probably revolved in a period of about three hours. At the