There is one plant belonging to tropical or sub-tropical climates that is peculiarly adapted by its mode of growth to the soil of these islands, and contributes greatly to their increase.  This is the Mangrove-tree.  Its seeds germinate in the calyx of the flower, and, before they drop, grow to be little brown stems, some six or seven inches long and about as thick as a finger, with little rootlets at one end.  Such Mangrove-seedlings, looking more like cigars than anything else, float in large numbers about the Reef.  I have sometimes seen them in the water about the Florida Reef in such quantities that one would have said some vessel laden with Havana cigars had been wrecked there, and its precious cargo scattered in the ocean.

In consequence of their shape and the development of the root, one end is a little heavier than the other, so that they float unevenly, with the loaded end a little lower than the lighter one.  When they are brought by the tide against such a cap of soil as I have described, they become stranded upon it by their heavier end, the rootlets attach themselves slightly to the soil, the advancing and retreating waves move the little plant up and down, till it works a hole in the sand, and having thus established itself more firmly, steadied itself as it were, it now stands upright, and, as it grows, throws out numerous roots, even from a height of several feet above the ground, till it has surrounded the lower part of its stem with a close net-work of roots.  Against this natural trellis or screen all sorts of materials collect; sand, mud, and shells are caught in it; and as these Mangrove-trees grow in large numbers and to the height of thirty feet, they contribute greatly to the solidity and compactness of the shores on which they are stranded.

Such caps of soil on the summit of a Coral Reef are of course very insecure till they are consolidated by a long period of accumulation, and they may even be swept completely away by a violent storm.  It is not many years since the light-house built on Sand Key for the greater security of navigation along the Reef was swept away with the whole island on which it stood.  Thanks to the admirably conducted Investigations of the Coast-Survey, this part of our seaboard, formerly so dangerous on account of the Coral Reefs, is now better understood, and every precaution has been taken to insure the safety of vessels sailing along the coast of Florida.

I cannot deny myself the pleasure of paying a tribute here to the high scientific character of the distinguished superintendent of this survey, who has known so well how to combine the most important scientific aims with the most valuable practical results in his direction of it.  If some have hitherto doubted the practical value of such researches,—­and unhappily there are always those who estimate intellectual efforts only by their material results,—­one would think that these doubts must be satisfied now that