FORMATION OF CORAL REEFS AND ISLANDS. 223 



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 zoophytes 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 a 

 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 debris 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 debris 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 zoo- 

 phytes growing over the reef-grounds, and of shells and other 

 relics of organic life, are constantly making ; and thus a bed 

 of coral debris 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 w r hole zoophyte. The coral debris and 

 shells fill up the intervals between the coral patches, and the 



