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On each of the
above days the line representing the great nocturnal
[page 37]
rise did not coincide with that of the great diurnal fall, so that narrow
ellipses were described, as is the usual rule with circumnutating organs.
The cotyledons are provided with a pulvinus, and its development will
hereafter be described.
Mimosa pudica (Leguminosae).--The cotyledons rise up vertically at night,
so as to close together. Two seedlings were observed in the greenhouse
(temp. 16o to 17o C. or 63o to 65o F.). Their hypocotyls were secured to
sticks, and glass filaments bearing little triangles of paper were affixed
to the cotyledons of both. Their movements were traced on a vertical glass
during 24 h. on November 13th. The pot had stood for some time in the same
position, and they were chiefly illuminated through the glass-roof. The
cotyledons of one of these seedlings moved downward in the morning till
11.30 A.M., and then rose, moving rapidly in the evening until they stood
vertically, so that in this case there was simply a single great daily fall
and rise.


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