Some very young seedlings were kept during two days in
the dark (temp. 57o - 59o F.) except when the circumnutation of their stems
was occasionally observed; and on the evening of the second day the
leaflets did not fully and properly go to sleep. The pot was then placed
for three days in a dark cupboard, under nearly the same temperature, and
at the close of this period the leaflets showed no signs of sleeping, and
were only slightly sensitive to a touch. On the following day the stem was
cemented to a
[page 378]
stick, and the movements of two leaves were traced on a vertical glass
during 72 h. The plants were still kept in the dark, excepting that at each
observation, which lasted 3 or 4 minutes,
Fig 158. Mimosa pudica: circumnutation and nyctitropic movement of a
leaflet (with pinna secured), traced on a vertical glass, from 8 A.M. Sept.
14th to 9 A.M. 16th.
they were illuminated by two candles. On the third day the leaflets still
exhibited a vestige of sensitiveness when forcibly pressed, but in the
evening they showed no signs of sleep. Nevertheless, their petioles
continued to circumnutate distinctly,
[page 379]
although the proper order of their movements in relation to the day and
night was wholly lost.
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