its tail in the effort to work the quicker. In
a short time the grub disappears and is at home. The point of entry,
minute, but always easily recognisable by its brown coloration on the
pale green background of the pea, has no fixed location; it may be at
almost any point on the surface of the pea, but an exception is usually
made of the lower half; that is, the hemisphere whose pole is formed by
the supporting stem.

It is precisely in this portion that the germ is found, which will not
be eaten by the larva, and will remain capable of developing into a
plant, in spite of the large aperture made by the emergence of the adult
insect. Why is this particular portion left untouched? What are the
motives that safeguard the germ?

It goes without saying that the Bruchus is not considering the gardener.
The pea is meant for it and for no one else. In refusing the few bites
that would lead to the death of the seed, it has no intention of
limiting its destruction. It abstains from other motives.

Let us remark that the peas touch laterally, and are pressed one
against the other, so that the grub, when searching for a point of
attack, cannot circulate at will. Let us also note that the lower pole
expands into the umbilical excrescence, which is less easy of
perforation than those parts protected by the skin alone. It is even
possible that the umbilicum, whose organisation differs from that of the
rest of the pea, contains a peculiar sap that is distasteful to the
little grub.

Such, doubtless, is the reason why the peas exploited by the Bruchus are
still able to germinate. They are damaged, but not dead, because the
invasion was conducted from the free hemisphere, a portion less
vulnerable and more easy of access. Moreover, as the pea in its entirety
is too large for a single grub to consume, the consumption is limited to
the portion preferred by the consumer, and this portion is not the
essential portion of the pea.

With other conditions, with very much smaller or very much larger seeds,
we shall observe very different results. If too small, the germ will
perish, gnawed like the rest by the insufficiently provisioned inmate;
if too large, the abundance of food will permit of several inmates.
Exploited in the absence of the pea, the cultivated vetch and the broad
bean afford us an excellent example; the smaller seed, of which all but
the skin is devoured, is left incapable of germination; but the large
bean, even though