ON THE DISPERSAL OF PLANTS. 279 
though ignorant agents in distributing over the islands the 
seeds and fruits of trees already established there, such as 
those of Cordia subcurdata, Hernandia peltata, and Morinda 
citrifolia. When these seeds germinate amongst the vegeta- 
tion in the interior of the islands, they often escape the 
attention of the crabs: whereas, when they attempt to sprout 
in full exposure on the beach, they can rarely evade thei 
notice, unless they are concealed by sand or pumice. : 
Since the occupation of these islands about 62 years ago, 
the frigate-birds, gannets, boobies, and other sea-birds, that 
once nested here in myriads, have been driven away; and in 
consequence one of the important agencies of seed distribu- 
tion no longer exists. So many disturbing elements, in fact, 
have been created in these islands, during their occupation 
by man, that even if the group was deserted for ages, the 
ancient condition of things could never be restored. By 
accident or design, a great number of strange plants have 
been brought here through human agency. A brief com- 
parison of the lists of the flora made by Mr. Darwin in 1836 
and by Mr. Forbes in 1878 will at once convince those 
interested in this subject that such is the case. But more 
important still, many mammals, birds, and new insects have 
been introduced accidentally or intentionally during the last 
half century, which have exercised a very noticeable disturb- 
ing influence in the plant-life of these islands. Sheep, deer, 
cats, rabbits, pigs, rats, fowls, &c., now play, or have recently 
played, an important part in the floral economy of this group 
by distributing some plants and exterminating others. For 
instance, as already observed, the fruits of Morinda citrifolia 
are eaten by sheep, deer, fowls, &c., and the seeds pass 
unharmed through their digestive canals.and are voided in a 
fit state for germination. Hence, the tree is spreading with 
great rapidity all over the islands, and is a cause of much 
trouble to the proprietor. In North Keeling Island the 
Papaw tree rapidly increases in numbers through the agency 
of fowls in a similar fashion. Ina like manner fowls have 
been the means of spreading another introduced plant, Canna 
indica. Some years ago, a cassowary that was kept on the 
Settlement Island, was a very efficient distributor of seeds. 
The fruits of Ochrosia parviflora were his especial favourites ; 
and, as a consequence, the undigested seeds were scattered 
everywhere, and the young trees became so numerous that 
they had to be destroyed. As an example of the manner in 
which the struggle for life amongst the animals may affect 
the survival of plants, I may refer to the circumstance that 
