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Of all the objects which the ocean casts upon its shores for the amusement of visitors from town, none are better than the heaps of coarse black sea-weed which some call "wrack," and some call "tang," and some know not what to call. Sea-weeds are classed in three groups—the red, the green, and the olive. The species under notice belongs to the last of these. When found lying upon the beach it certainly looks as much like black as a lump of charcoal, but when growing in the sea is as decidedly olive. But we are speaking of it as though there were but one species, whereas two, three, or four, are often mingled in the same heap, and our object is to point out the differences, and furnish names whereby they may be distinguished.

First, there is the Black Tang, or Bladder-wrack (Fucus vesiculosus), with long fronds sometimes two

or three feet in length, forking again and again into what we may call branches, with a stout midrib running down the centre, and covered with warty tubercules, or bladders, arranged in pairs (fig. 1). These are hollow, and filled with air, so as to render the "wrack" buoyant in the water. The tips of the fronds will sometimes be noticed swollen, and covered with little tubercles, scarcely raised above the surface. These contain the fructification. Let us pause a moment to examine them more minutely. We shall observe that each of these little frustules has a minute opening through which their contents escape. Cut one of these tips across, and each frustule will be seen to represent a cell or internal cavity (fig. 2, a), enclosing, in one plant, what are called the antheridia and in another the spores. The former of these we may regard as the male, and the latter as the female organs. Both are always produced on separate plants. The antheridia are little bags or vesicles, containing small bodies called zoospores (b), which no sooner escape than they move about in the water as if endowed with life, and conduct themselves like little animals. The spores are little grains, of an oblong shape, which ultimately separate into a definite number of parts (c); these perform the functions of seeds, which are fertilized by the zoospores, as the ovules are fertilized by the pollen of flowering plants. We cannot, within our present limits, enter upon the mysteries of increase and multiplication in sea-weeds, but must content ourselves with indicating what any good book on the subject will more fully explain.

The Serrated Wrack (Fucus serratus) resembles

the last in form, but there are no air-bladders, and the edges of the fronds are jagged or serrated, like the teeth of a saw (fig. 2). In like manner the fruit