for the fact of a still larger proportion of the laburnum leaves not
having been drawn in by the base, by worms having acquired the habit of
generally drawing in leaves by their tips and thus avoiding the
foot-stalk. For the basal margin of the blade in many kinds of leaves
forms a large angle with the foot-stalk; and if such a leaf were drawn in
by the foot-stalk, the basal margin would come abruptly into contact with
the ground on each side of the burrow, and would render the drawing in of
the leaf very difficult.
Nevertheless worms break through their habit of avoiding the foot-stalk,
if this part offers them the most convenient means for drawing leaves
into their burrows. The leaves of the endless hybridised varieties of
the Rhododendron vary much in shape; some are narrowest towards the base
and others towards the apex. After they have fallen off, the blade on
each side of the midrib often becomes curled up while drying, sometimes
along the whole length, sometimes chiefly at the base, sometimes towards
the apex. Out of 28 fallen leaves on one bed of peat in my garden, no
less than 23 were narrower in the basal quarter than in the terminal
quarter of their length; and this narrowness was chiefly due to the
curling in of the margins. Out of 36 fallen leaves on another bed, in
which different varieties of the Rhododendron grew, only 17 were narrower
towards the base than towards the apex. My son William, who first called
my attention to this case, picked up 237 fallen leaves in his garden
(where the Rhododendron grows in the natural soil) and of these 65 per
cent. could have been drawn by worms into their burrows more easily by
the base or foot-stalk than by the tip; and this was partly due to the
shape of the leaf and in a less degree to the curling in of the margins:
27 per cent. could have been drawn in more easily by the tip than by the
base: and 8 per cent. with about equal ease by either end. The shape of
a fallen leaf ought to be judged of before one end has been drawn into a
burrow, for after this has happened, the free end, whether it be the base
or apex, will dry more quickly than the end imbedded in the damp ground;
and the exposed margins of the free end will consequently tend to become
more curled inwards than they were when the leaf was first seized by the
worm. My son found 91 leaves which had been dragged by worms into their
burrows, though not to a great depth; of these 66 per cent. had been
drawn in by the base or foot-stalk; and 34 per cent. by the tip. In this
case, therefore, the worms judged with a considerable degree of
correctness how best to draw the withered leaves of this foreign plant
into their burrows; notwithstanding that they had to depart from their
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