Along those stretches of beach where the sea has taken stones and boulders and deposited them offshore, storms sometimes bring in fairly large quantities of seaweed, which need beds of stone for their attachment. The fucus or rockweed, the laminaria or kelp, and some of the “red” algae like Irish moss which are among the more common kinds found along the beach, have no roots, since the plants take all their nourishment from the sea water that surrounds them, but are anchored by holdfasts, stubby structures which in the laminaria may look like the exposed, above-ground roots of some tropical trees, and in the fucus a round expansion of the tissues at its base, which is strongly and tightly sealed to the surface of rocks and stones. Everything about these weeds, with divided, narrow, or tapering fronds to resist being torn by the waves, with bladders serving as floats, with gelatinous surfaces, with hollow stems, are eloquent of the nature of salt water, its ebb and flow, its depths, its capacious circulation. The seaweeds found on the beach, black, thin, dried out, or fresh and slippery, olive green, brown, or red, having been torn loose by a storm, start growing beyond the violent action of the surf, and grow for the most part to a depth of some forty or fifty feet. Different varieties like different depths, but since they are not free floating unless torn loose they are not found beyond the point where rays of sunlight, necessary for manufacturing food, cannot reach them. Over and beyond them, in surface waters where the light penetrates before being absorbed, is a vegetation, varying in abundance according to place and season, but of incredible numbers over all, the one-celled microscopic organisms that are the basic food of all the seas. The seaweeds are simple and primitive in structure compared with much of the plant life on land, the more hazardous, contrary environment, and the members of the phytoplankton (the planktonic plants), even more so, although the diatoms, which form a large part of it, show a variety of outer form. Each diatom has a skeleton, made largely of silica, an outer shell hard enough to resist easy dissolution when the plant dies. It is formed like a pillbox, or a casket, or it is shaped like a quill, a ribbon, or rod, or it is joined with others in beads and chains. Each is minute, an etched, crystalline perfection, and each is lost in other billions, which we might only see on occasion as a green or greenish-brown stain across the water.