e soil, but to
enable them to flee from the great number of their own kind, and from
their enemies among animals and parasitic plants. The adventurers
among plants often meet with the best success, not because the seeds
are larger, or stronger, or better, but because they find, for a time,
more congenial surroundings. We must not overlook the fact, so well
established, that one of the greatest points to be gained by plant
migration is to enable different stocks of a species to be cross
fertilized, and thereby improved in vigor and productiveness.

55. Fruit grown in a new country is often fair.--Every horticulturist
knows that apples grown in a new country, that is suited to them,
are healthy and fair; but, sooner or later, the scab, and codling
moth, and bitter rot, and bark louse arrive, each to begin its
particular mode of attack. Peach trees in new places, remote from
others, are often easily grown and free from dangers; but soon will
arrive the yellows, borers, leaf curl, rot, and other enemies. For
a few years plums may be grown, in certain new localities, without
danger from curculio, or rot, or shot-hole fungus. It has long been
known that the nicest way to grow a few cabbages, radishes, squashes,
cucumbers, or potatoes is to plant a few here and there in good soil,
at considerable distances from where any have heretofore been grown.
For a time enemies are not likely to find them. I have often noticed
that, while pear-blight decimated or swept large portions of a pear
orchard, a few isolated trees, scattered about the neighborhood,
usually remain healthy. The virgin soil of the Dakotas produced, at
a trifling cost, healthy, clean wheat, but it was not long before
the Russian thistle, false flax, and other pests followed, to contest
their rights to the soil.

As animals starve out, in certain seasons when food is scarce, or
more likely migrate to regions which can afford food, so plants desert
worn-out land and seek fresh fields. As animals retreat to secluded
and isolated spots to escape their enemies, so, likewise, many plants
accomplish the same thing by sending out scouts in all directions
to find the best places; these scouts, it is needless to say, are
seeds, and when they have found a good place, they occupy it, without
waiting for further instructions.

56. Much remains to be discovered.--"In this, as in other branches
of science, we have made a beginning. We have learned just enough
to perceive how l