228 FORMATION OF CORAL REEFS AND ISLANDS. 
upon the land; there are large areas that bear nothing, and 
others of great extent that are thickly overgrown. There is, 
however, no green sward to the landscape; sand and frag- 
ments fill up the bare intervals between the flowering tufts: 
or, where the zodphytes are crowded, there are deep holes 
among the stony stems and folia. 
These fields of growing coral spread over submarine 
lands, such as the shores of islands and continents, where the 
depth is not greater than theirhabits require, just as vegetation 
extends itself through regions that are congenial. The germ 
or ovule, which, when first produced, is free, finds afterward « 
point of rock, or dead coral, or some support, to plant itself 
upon, and thence springs the tree or other forms of coral growth. 
The analogy to vegetation does not stop here. It is well 
known that the débris of the forest, decaying leaves and 
stems, and animal remains, add to the soil; that in the marsh 
or swamp—where decaying vegetation is mostly under water, 
and sphagnous mosses grow luxuriantly, ever alive and flour- 
ishing at top, while dead and dying below,—accumulations 
of such débris are ceaselessly in progress, and deep beds of 
peat are formed. Similar is the history of the coral mead. 
Accumulations of fragments and sand from the coral zo6- 
phytes growing over the reef-grounds, and of shells and other 
relics of organic life, are constantly making; and thus a bed 
of coral débris is formed and compacted. ‘There is this dif- 
ference, that a large part of the vegetable material consists of 
elements which escape as gases on decomposition, so that there 
is a great loss in bulk of the gathered mass; whereas coral is 
an enduring rock material undergoing no change except the 
mechanical one of comminution. The animal portion is but 
a mere fraction of the whole zodphyte. The coral débris and 
shells fill up the intervals between the coral patches, and the 
