224 THE FISHERIES OF THE UNITED STATES. 



several hundred yards long and forty or fifty yards in breadth. You may count up the number of individual oysters, 

 Tvhen I tell you that a square foot will often contain a hundred. 



When the reef has attained such a height that its crest is exposed to the air at low tide longer than it is visited 

 by the water of the high tide, the oysters will cease to grow there, while still flourishing around the edges. The 

 dead shells, growing brittle, are soon broken to pieces by the waves, and finally reduced to such small fragments, 

 that they are like a shingle beach, or even like sand. Such a reef also, opposing the flow of the currents, furnishes 

 lodgment to all sorts of cU-ifting sea-wrack, receives a growth of the algse and grasses which frequent such half- 

 submerged levels, and is all the time built up at the top by the washing upon it of fragments broken from its edges. 

 It is not long, therefore, before a sort of shelly soil is formed, and some floating mangrove stem or seed takes root 

 there, and manages to get so firm a foothold that the storms do not tear it away. 



The oyster as a reef-buildek. — This done, the f;ir-reaching and tangled roots of the bush form an eddy 

 which deposits sand and floating stuft', until more mangroA'es have room to root themselves, and the bar ceases to be 

 a "reef"; it has become a "mangrove key". Now, the mangrove (of which there are several kinds) is a very curious 

 tree. It has a low, branching stem, and is thus pretty much all head ; you cannot see anything as yoii approach 

 but a compact mass of brightly green, thick, shining leaves, trailing to the ground. A nearer view discloses another 

 very curious feature. From the main trunk, near the ground, extend out on all sides, and at varying height, some 

 branches which do not go upward and bear leaves, but turn downward, enter the ground, and become roots. There 

 are dozens of these stays surrounding every stem, and holding it, like so many cables, against the fury of the storms 

 which sometimes hurl both wind and waves against the groves. But this is not all. Every low branch produces a 

 considerable number of thick, leafless, straight twigs, which elongate straight downward through air and water, until 

 they penetrate the soil and become rooted. The mangrove is not only braced upon a score of roots, therefore, but 

 anchored from everyone of its lower and larger arms. A perfect tangle and net- work of these roots and rooted 

 stems tlius suiTOund each tree and every islet with an abatis often several rods in width. 



Such a network speedily verifies its likeness to a basket by catching outside matter. Along the solid edges 

 of the key itself, and everywhere in the neighborhood, are living oysters which animally send forth a cloud of 

 young to seek new quarters. The mangrove stems afford capital resting-places, and speedily become encased in 

 oysters which increase in size and number very rapidly. This suspended kind is known as the "mangrove 

 oyster"; but I do not see that they are anything but progeny of the coon bars. Barnacles, too, in vast numbers, 

 muscles, bryozoa, and many forms of minute water-animals cling to these half-submerged branches or flourish 

 under their shelter, -^Yhere the hard sand and the bare angles of oyster-rock are being buried under a coating of 

 mud and decayed vegetation, which the basket-work of mangrove roots and salt-grass has caught and confined. 



An especially noteworthy member of such a colony is a marine worm of small size, which forms about itself a 

 tubular, twisted case of lime very like that of the serpula. Along certain portions of the coast, south of Tampa 

 bay, these worms are extremely numerous ; and they build up their cases so closely together that they join one 

 another, and so cover the foundation upon which they grow with limy tubes somewhat larger than a darning-needle, 

 the partially coiled bases of which are in unison, but the enpurpled mouths a fraction of an inch apart from one 

 another, forming a solid mass of lime with a bristling (and, at high tide, very animated and beautiful) surface. 

 Without being sure that I am right, I suspect that these worms survive only a single year, and then dying, leave 

 their indestructible cases to serve as the foundation upon which their progeny may rear their tier of tubes. Thus, 

 by the additions of successive generations (as in the case of the coral-growth, only through a different history), this 

 worm-structure increases into an extensive mass of heavy rock. I have seen pieces many yards square and two 

 feet or more thick. Growing irregularly, its crannies aftbrd a haunt for many species of mollusks and crustaceans 

 that like to hide away in holes; and its mass is further enlarged by the growth of bunches of oysters and the filling 

 of all its interstices with sand and broken shells, which become solidified along with the worm-tubes by the 

 production of a native cement. Thus millions of tons of solid limestone, most useful for building purposes, is 

 every decade added to the Floridian coast by despised worms. 



Attracted by the excellence of the hiding-places offered, and by the abundance of " small deer" lurking there, 

 come to the mangrove roots many predatory sorts of aquatic animals in search of food — couchs, whelks, boring 

 sea-snails, crabs of several species, and mollusk-eatiug fish, bke the sheep's-head. Where there is teeming life, 

 death is frequent, and thousands of emi)ty shells and fleshless skeletons sink into the animated ooze, and rapiiUy 

 fill it up, until the water no longer covers it, except at the highest tide, and then leaves an important toll of drift- 

 wood, and the adventurous water-loving mangroves must push their roots farther and farther into the sea. 



Meanwhile a similar process has been raising the center of the island. Decay of grass and salt weeds, and 

 mangroves and drifted wood finally brings a surface permanently above the water. Huge flocks of water-birds 

 daily alight upon it to rest and teed, and their droppings increase and enrich the soil. Various seeds are wafted or 

 floated from the mainland and build up its stock of vegetation; various land animals, chiefly reptilian, make the 

 new key their home. They die and are buried there. The simple mangrove swamp is succeeded by an intermixture 

 of oak, pine, and palmetto, and their rotting logs gradually make a wide extent of solid ground. Discovering this, 

 Indians get into the habit of landing there to open and feast upon oysters, clams, and conchs, and from the debris 



