Whether the rising of the glass filament
which was attached to the back of the leaf, resulted from its margin
becoming slightly inflected (as generally occurs), or from the rising of
the petiole, was not ascertained.
In order to learn whether the tentacles or gland-bearing hairs
circumnutate, the back of a young leaf, with the innermost tentacles as yet
incurved, was firmly cemented with shellac to a flat stick driven into
compact damp argillaceous sand. The plant was placed under a microscope
with the stage removed and with an eye-piece micrometer, of which each
division equalled 1/500 of an inch. It should be stated that as the leaves
grow older the tentacles of the exterior rows bend outwards and downwards,
so as ultimately to become deflected considerably beneath the horizon. A
tentacle in the second row from the margin was selected for observation,
and was found to be moving outwards at a rate of 1/500 of an inch in 20 m.,
or 1/100 of inch in 1 h. 40 m.; but as it likewise moved from side to side
to an extent of above 1/500 of inch, the movement was probably one of
modified circumnutation.
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