M. to 3 P.M. at a high
but varying temperature (viz., between 72o and 83o F.) a leaflet (with the
petiole secured) circumnutated rapidly, for it made three large vertical
ellipses in the course of the six hours. According to Brongniart, Marsilea
pubescens sleeps like the present species. These plants are the sole
cryptogamic ones known to sleep.]
Summary and Concluding Remarks on the Nyctitropic or Sleep-movements of
Leaves.--That these movements are in some manner of high importance to the
plants which exhibit them, few will dispute who have observed how complex
they sometimes are. Thus with Cassia, the leaflets which are horizontal
during the day not only bend at night vertically downwards with the
terminal pair directed considerably backwards, but they also rotate on
their own axes, so that their lower surfaces are turned outwards. The
terminal leaflet of Melilotus likewise rotates, by which movement one of
its lateral edges is directed upwards, and at the same time it moves either
to the left or to the right, until its upper surface comes into contact
with that of the lateral leaflet on the same side, which has likewise
rotated on its own axis.
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