XII 
GEOGRAPHICAL DISTRIBUTION OF ORGANISMS 
361 
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 after¬ 
wards 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 experi¬ 
ment 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 proves that 
