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4 inch in length (measured as
before) and .82 in breadth, they became greatly depressed. In one case they
were horizontal at noon, and at 10 P.M. one of them stood at 64o and the
other at 47o beneath the horizon. The blades are thin, and the petioles,
which become much curved down at night, are short, so that here weight can
hardly have produced any effect. With all the above species of Ipomoea,
when the two cotyledons on the same seedling were unequally depressed at
night, this seemed to depend on the position which they had held during the
day with reference to the light.
Solanum lycopersicum (Solaneae).--The cotyledons rise so much at night as
to come nearly in contact. Those of 'S. palinacanthum' were horizontal at
noon, and by 10 P.M. had risen only 27o 30 minutes; but on the following
morning before it was light they stood at 59o above the horizon, and in the
afternoon of the same day were again horizontal. The behaviour of the
cotyledons of this latter species seems, therefore, to be anomalous.
[page 307]
Mirabilis jalapa and longiflora (Nyctagineae).


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