lture, one hundred and eight species are of foreign origin.
Three notable samples of weeds in the United States have gone from
the west to the east, carried in seeds of grasses or clovers. These
are _Rudbeckia hirta_, _Artemisia biennis_, _Plantago aristata_. To
these Mr. Dewey adds buffalo bur, _Solanum rostratum_, squirreltail,
_Hordeum jubatum_, false ragweed or marsh elder, _Iva xanthifolia_,
_Franseria hookeriana_, alfalfa dodder, _Cuscuta epithymum_.

Above I have barely mentioned a few of the methods by which man is
an unwilling agent in distributing plants. Large volumes could be
filled with statements of man's more or less carefully planned
attempts to transport seeds and living plants from one part of the
world to another.

CHAPTER IX.
SOME REASONS FOR PLANT MIGRATION.

53. Plants are not charitable beings.--Man uses to his advantage a
large number of plants, but there appears to be no evidence that the
schemes for their dispersion were designed for anything except to
benefit the plants themselves. The elegant foliage and beautiful
flowers, the great diversity of attractive seeds and fruits, all
point to plants as strictly selfish beings, if I may so use the term;
and not to plants as works of charity, to be devoured by animals
without any compensation. By fertilizing flowers, by distributing
plants, and by other helpful acts, animals pay for at least a portion
of the damage they do.

By an almost infinite number of devices, we have seen that seeds and
fruits flee from the parental spot on the wings of the wind, float
on currents of ocean, lake, and river. They are shot by bursting pods
and capsules in every direction. With hooks, barbs, and glands they
cling to the covering of animals. Allured by brilliant colors, birds
and other animals seek and devour the fruits of many plants, the seeds
of which are preserved from harm by a solid armor; these seeds are
then sown broadcast over the land, ready to start new colonies. Nuts
are often carried by squirrels for long distances, and there securely
buried, a few in a place. By a slow process, which, however, covers
a considerable space, in a few years many plants send forth roots,
rootstalks, stolons, and runners, and thus increase their
possessions or find new homes.

54. Plants migrate to improve their condition.--The various devices
by which plants are shifted from place to place are not merely to
extend and multiply the species, and reach a fertil