exposed to the weather for eight additional weeks had not become more
disintegrated or decayed near the base than elsewhere. It is thus
evident that the thick basal end of the petiole is drawn in not solely
for the sake of plugging up the mouths of the burrows, but as food. Even
the narrow truncated tips of some few petioles had been gnawed; and this
was the case in 6 out of 37 which were examined for this purpose. Worms,
after having drawn in and gnawed the basal end, often push the petioles
out of their burrows; and then drag in fresh ones, either by the base for
food, or by the apex for plugging up the mouth more effectually. Thus,
out of 37 petioles inserted by their tips, 5 had been previously drawn in
by the base, for this part had been gnawed. Again, I collected a handful
of petioles lying loose on the ground close to some plugged-up burrows,
where the surface was thickly strewed with other petioles which
apparently had never been touched by worms; and 14 out of 47 (_i.e._
nearly one-third), after having had their bases gnawed had been pushed
out of the burrows and were now lying on the ground. From these several
facts we may conclude that worms draw in some petioles of the ash by the
base to serve as food, and others by the tip to plug up the mouths of
their burrows in the most efficient manner.
The petioles of _Robinia pseudo-acacia_ vary from 4 or 5 to nearly 12
inches in length; they are thick close to the base before the softer
parts have rotted off, and taper much towards the upper end. They are so
flexible that I have seen some few doubled up and thus drawn into the
burrows of worms. Unfortunately these petioles were not examined until
February, by which time the softer parts had completely rotted off, so
that it was impossible to ascertain whether worms had gnawed the bases,
though this is in itself probable. Out of 121 petioles extracted from
burrows early in February, 68 were imbedded by the base, and 53 by the
apex. On February 5 all the petioles which had been drawn into the
burrows beneath a Robinia, were pulled up; and after an interval of
eleven days, 35 petioles had been again dragged in, 19 by the base, and
16 by the apex. Taking these two lots together, 56 per cent. were drawn
in by the base, and 44 per cent. by the apex. As all the softer parts
had long ago rotted off, we may feel sure, especially in the latter case,
that none had been drawn in as food. At this season, therefore, worms
drag these petioles into their burrows indifferently by either end, a
slight preference being given to the base. This latter fact may be
accounted for by the difficulty of plugging up a burrow with objects so
extremely thin as are the upper ends. In support of this view, it may be
38