190 CORALS AND CORAL LSLANDS. 



grow scattered over the surface, like vegetation 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 fragments 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 their habits require, just as vegetation ex- 

 tends 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 flourishing 

 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. Accumu- 

 lations of fragments and sand from the coral zoophytes grow- 

 ing over the reef-grounds, and of shells and other refics of 

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

 debris is formed and compacted. There is this difference, 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 zoophyte. The coaal debris and 

 shells fill up the intervals between the coral patches and the 

 cavities among the living tufts, and in this manner produce the 

 reef deposit ; and the bed is finally consolidated while still 

 beneath the water. 



