The
four pinnae also approach each other closely, and the whole leaf is thus
rendered very compact. The main petiole sinks downwards during the day till
late in the evening, and rises until very early in the morning. The stem is
continually circumnutating at a rapid rate, though not to a wide extent.
Some very young plants, kept in darkness, were observed during two days,
and although subjected to a rather low temperature of 57o - 59o F., the
stem of one described four small ellipses in the course of 12 h. We shall
immediately see that the main petiole is likewise continually
circumnutating, as is each separate pinna and each separate leaflet.
Therefore, if the movement of the apex of any one leaflet were to be
traced, the course described would be compounded of the movements of four
separate parts.
[page 375]
A filament had been fixed on the previous evening, longitudinally to the
main petiole of a nearly full-grown, highly-sensitive leaf (four inches in
length), the stem having been secured to a stick at its base; and a tracing
was made on a vertical glass in the hot-house under a high temperature.
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