p into the higher regions of the atmosphere, where
they are liable to be caught by strong winds, and thus conveyed enormous
distances over seas or continents. With such powerful means of
dispersal the distribution of insects over the entire globe, and their
presence in the most remote oceanic islands, offer no difficulties.

_The Dispersal of Plants._

The dispersal of seeds is effected in a greater variety of ways than are
available in the case of any animals. Some fruits or seed-vessels, and
some seeds, will float for many weeks, and after immersion in salt water
for that period the seeds will often germinate. Extreme cases are the
double cocoa-nut of the Seychelles, which has been found on the coast of
Sumatra, about 3000 miles distant; the fruits of the Sapindus saponaria
(soap-berry), which has been brought to Bermuda by the Gulf Stream from
the West Indies, and has grown after a journey in the sea of about 1500
miles; and the West Indian bean, Entada scandens, which reached the
Azores from the West Indies, a distance of full 3000 miles, and
afterwards germinated at Kew. By these means we can account for the
similarity in the shore flora of the Malay Archipelago and most of the
islands of the Pacific; and from an examination of the fruits and seeds,
collected among drift during the voyage of the _Challenger_, Mr. Hemsley
has compiled a list of 121 species which are probably widely dispersed
by this means.

A still larger number of species owe their dispersal to birds in several
distinct ways. An immense number of fruits in all parts of the world are
devoured by birds, and have been attractively coloured (as we have
seen), in order to be so devoured, because the seeds pass through the
birds' bodies and germinate where they fall. We have seen how frequently
birds are forced by gales of wind across a wide expanse of ocean, and
thus seeds must be occasionally carried. It is a very suggestive fact,
that all the trees and shrubs in the Azores bear berries or small fruits
which are eaten by birds; while all those which bear larger fruits, or
are eaten chiefly by mammals--such as oaks, beeches, hazels, crabs,
etc.--are entirely wanting. Game-birds and waders often have portions of
mud attached to their feet, and Mr. Darwin has proved by experiment that
such mud frequently contains seeds. One partridge had such a quantity of
mud attached to its foot as to contain seeds from which eighty-two
plants germinated; this prove