incurvation. On the contrary, the margin became somewhat reflexed, as
if injured, and so remained for the three following days, as long as it
was observed.
Experiment 5. A large fragment of a fly was placed halfway between the
apex and base of a leaf and halfway between the midrib and one margin.
A short space of this margin, opposite the fly, showed a trace of
incurvation after 3 hrs., and this became strongly pronounced in 7 hrs.
After 24 hrs. the infolded edge was only .16 of an inch (4.064 mm.)
from the midrib. The margin now began to unfold, though the fly was
left on the leaf; so that by the next morning (i.e. 48 hrs. from the
time when the fly was first put on) the infolded edge had almost
completely recovered its original position, being now .3 of an inch
(7.62 mm.), instead of .16 of an inch, from the midrib. A trace of
flexure was, however, still visible.
Experiment 6. A young and concave leaf was selected with its margins
slightly and naturally incurved. Two rather large, oblong, rectangular
pieces of roast meat were placed with their ends touching the infolded
edge, and .46 of an inch (11.68 mm.) [page 373] apart from one another.
After 24 hrs. the margin was greatly and equally incurved (see fig. 16)
throughout this space, and for a length of .12 or .13 of an inch (3.048
or 3.302 mm.) above and below each bit; so that the margin had been
affected over a greater length between the two bits, owing to their
conjoint action, than beyond them. The bits of meat were too large to
be clasped by the margin, but they were tilted up, one of them so as to
stand almost vertically. After 48 hrs. the margin was almost unfolded,
and the bits had sunk down. When again examined after two days, the
margin was quite unfolded, with the exception of the naturally
inflected edge; and one of the bits of meat, the end of which had at
first touched the edge, was now .067 of an inch (1.70 mm.) distant from
it; so that this bit had been pushed thus far across the blade of the
leaf.
FIG. 16. (Pinguicula vulgaris.) Outline of leaf, with right margin
inflected against two square bits of meat.
Experiment 7. A bit of meat was placed close to the incurved edge of a
rather young leaf, and after it had re-expanded, the bit was left lying
.11 of an inch (2.795 mm.) from the edge. The distance from the edge to
320