M. It
should be observed that none of the leaves described in this chapter
(except, as we believe, those of Lupinus speciosus) possess a pulvinus; for
the periodical movements of leaves thus provided have generally been
amplified into so-called sleep-movements, with which we are not here
concerned. The fact of leaves and cotyledons frequently, or even generally,
rising a little in the evening and sinking in the morning, is of interest
as giving the foundation from which the specialised sleep-movements of many
leaves and cotyledons, not provided with a pulvinus, have been developed.
the above periodicity should be kept in mind, by any one considering the
problem of the horizontal position of leaves and cotyledons during the day,
whilst illuminated from above.
[page 263]
CHAPTER V.
MODIFIED CIRCUMNUTATION: CLIMBING PLANTS; EPINASTIC AND HYPONASTIC
MOVEMENTS.
Circumnutation modified through innate causes or through the action of
external conditions--Innate causes--Climbing plants; similarity of their
movements with those of ordinary plants; increased amplitude; occasional
points of difference--Epinastic growth of young leaves--Hyponastic growth
of the hypocotyls and epicotyls of seedlings--Hooked tips of climbing and
other plants due to modified circumnutation--Ampelopsis tricuspidata--
Smithia Pfundii--Straightening of the tip due to hyponasty--Epinastic
growth and circumnutation of the flower-peduncles of Trifolium repens and
Oxalis carnosa.
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