and covered with a net which allowed the free entrance of air, were left
out of doors for several nights, and now 72 leaves were all properly
drawn in by their bases.
It might perhaps be inferred from the facts as yet given, that worms
somehow gain a general notion of the shape or structure of pine-leaves,
and perceive that it is necessary for them to seize the base where the
two needles are conjoined. But the following cases make this more than
doubtful. The tips of a large number of needles of _P. austriaca_ were
cemented together with shell-lac dissolved in alcohol, and were kept for
some days, until, as I believe, all odour or taste had been lost; and
they were then scattered on the ground where no pine-trees grew, near
burrows from which the plugging had been removed. Such leaves could have
been drawn into the burrows with equal ease by either end; and judging
from analogy and more especially from the case presently to be given of
the petioles of _Clematis montana_, I expected that the apex would have
been preferred. But the result was that out of 121 leaves with the tips
cemented, which were drawn into burrows, 108 were drawn in by their
bases, and only 13 by their tips. Thinking that the worms might possibly
perceive and dislike the smell or taste of the shell-lac, though this was
very improbable, especially after the leaves had been left out during
several nights, the tips of the needles of many leaves were tied together
with fine thread. Of leaves thus treated 150 were drawn into burrows 123
by the base and 27 by the tied tips; so that between four and five times
as many were drawn in by the base as by the tip. It is possible that the
short cut-off ends of the thread with which they were tied, may have
tempted the worms to drag in a larger proportional number by the tips
than when cement was used. Of the leaves with tied and cemented tips
taken together (271 in number) 85 per cent. were drawn in by the base and
15 per cent. by the tips. We may therefore infer that it is not the
divergence of the two needles which leads worms in a state of nature
almost invariably to drag pine-leaves into their burrows by the base.
Nor can it be the sharpness of the points of the needles which determines
them; for, as we have seen, many leaves with the points cut off were
drawn in by their bases. We are thus led to conclude, that with
pine-leaves there must be something attractive to worms in the base,
notwithstanding that few ordinary leaves are drawn in by the base or
foot-stalk.
_Petioles_. We will now turn to the petioles or foot-stalks of compound
36