N.W., and that of the other N.N.E. The terminal leaflet behaves
differently, for it twists to either side, the upper surface facing
sometimes east and sometimes west, but rather more commonly west than east.
The terminal leaflet also moves in another and more remarkable manner, for
whilst its blade is twisting and becoming vertical, the whole leaflet bends
to one side, and invariably to the side towards which the upper surface is
directed; so that if this surface faces the west the whole leaflet bends to
the west, until it comes into contact with the upper and vertical surface
of the western lateral leaflet. Thus the upper surface of the terminal and
of one of the two lateral leaflets is well protected.
The fact of the terminal leaflet twisting indifferently to either
* 'Annales des Sc. Nat. Bot.' (5th series), ix. 1868, p. 368.
[page 346]
side and afterwards bending to the same side, seemed to us so remarkable,
that we endeavoured to discover the cause. We imagined that at the
commencement of the movement it might be determined by one of the two
halves of the leaflet being a little heavier than the other.
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