Thus one main
petiole was observed to rise at night 59o, whilst three others rose only 7o
and 9o. The petioles and sub-petioles are continually circumnutating during
the whole 24 h., as we shall presently see.
The leaves of the following 15 species, M. officinalis, suaveolens,
parviflora, alba, infesta, dentata, gracilis, sulcata, elegans, coerulea,
petitpierreana, macrorrhiza, Italica, secundiflora, and Taurica, sleep in
nearly the same manner as just described; but the bending to one side of
the terminal leaflet is apt to fail unless the plants are growing
vigorously. With M. petitpierreana and secundiflora the terminal leaflet
was rarely seen to bend to one side. In young plants of M. Italica it bent
in the usual manner, but with old plants in full flower, growing in the
same pot and observed at the same hour, viz., 8.30 P.M., none of the
terminal leaflets on several scores of leaves had bent to one side, though
they stood vertically; nor had the two lateral leaflets, though standing
vertically, moved towards the terminal one. At 10.30 P.M., and again one
hour after midnight, the terminal leaflets had become very slightly bent to
one side, and the lateral leaflets had moved a very little towards the
terminal one, so that the position of the leaflets even at this late hour
was far from the ordinary one.
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