and during the day is 2 hrs. 8 m. for each revolution; and none of
the revolutions varied much from this rate. The revolving movement
continues as long as the plant continues to grow; but each separate
internode, as it becomes old, ceases to move.

To ascertain more precisely what amount of movement each internode
underwent, I kept a potted plant, during the night and day, in a
well-warmed room to which I was confined by illness. A long shoot
projected beyond the upper end of the supporting stick, and was
steadily revolving. I then took a longer stick and tied up the
shoot, so that only a very young internode, 1.75 of an inch in
length, was left free. This was so nearly upright that its
revolution could not be 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 a second revolution in 9
hrs.; 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 hrs. As on the succeeding morning I found that the
shoot revolved in 2 hrs. 45 m., it must have made during the night
four revolutions, each at the average rate of a little over 3 hrs. I
should add that the temperature of the room varied only a little.
The shoot had now grown 3.5 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 hrs. 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 completed;