plants, some of which naturalize themselves. Of
this I will cite a striking example. There is, at the gate of
Montpellier, a meadow set apart for drying foreign wool, _after it has
been washed_. There hardly passes a year without foreign plants being
found naturalized in this drying-ground. I have gathered there
_Centaurea parviflora_, _Psoralea palaestina_, and _Hypericum crispum_."
This fact is not only illustrative of the aid which man lends
inadvertently to the propagation of plants, but it also demonstrates the
multiplicity of seeds which are borne about in the woolly and hairy
coats of wild animals.

The same botanist mentions instances of plants naturalized in seaports
by the ballast of ships; and several examples of others which have
spread through Europe from botanical gardens, so as to have become more
common than many indigenous species.

It is scarcely a century, says Linnaeus, since the Canadian erigeron, or
flea-bane, was brought from America to the botanical garden at Paris;
and already the seeds have been carried by the winds so that it is
diffused over France, the British islands, Italy, Sicily, Holland, and
Germany.[868] Several others are mentioned by the Swedish naturalist, as
having been dispersed by similar means. The common thorn-apple (_Datura
Stramonium_), observes Willdenow, now grows as a noxious weed throughout
all Europe, with the exception of Sweden, Lapland and Russia. It came
from the East Indies and Abyssinia to us, and was thus universally
spread by certain quacks, who used its seeds as an emetic.[869] The same
plant is now abundant throughout the greater part of the United States,
along road-sides and about farm-yards. The yellow monkey-flower,
_Mimulus luteus_, a plant from the north-west region of America, has now
established itself in various parts of England, and is spreading
rapidly.

In hot and ill-cultivated countries, such naturalization takes place
more easily. Thus the _Chenopodium ambrosioides_, sown by Mr. Burchell
on a point of St. Helena, multiplied so fast in four years as to become
one of the commonest weeds in the island, and it has maintained its
ground ever since 1845.[870]

The most remarkable proof, says De Candolle, of the extent to which man
is unconsciously the instrument of dispersing and naturalizing species,
is found in the fact, that in New Holland, America, and the Cape of Good
Hope, the aboriginal European species exceed in number all the others
whic