nourishment enters by the thin outside layer. In all sea-water there is some organic stuff or sea soup, the result of the decomposition of tiny things, and there is some air in the water which contains oxygen and nitrogen and carbonic acid. Under the influence of life, the organic stuff is absorbed by the cell-membrane, and is rendered useful to the rest of the plant, into whose cells, not quite walled up by carbonate of lime, it enters like sap, and circulates. The carbonate of lime can only get in by there being some minute quantity in the sea-water, and there is sufficient in the chalky spots and limestone shores, not only dissolved by the sea-water, but held in suspension by it. The water is ever on the move, passing over the coralline, and in a few weeks a few grains, for they make a great show, are absorbed and deposited in it. Small sea-snails browse on the corallines, and have to thank them for their lime, which is necessary for their shell. There are some other plants found at low-tide marks which are calcareous, but instead of being jointed, like the corallines, they form irregular and rounded little blocks, or simple papery-looking expansions on some of the larger-leaved sea-weeds. They are usually white and hard, and no one would consider them to be of a vegetable nature were their microscopic anatomy not known. They have a great resemblance in mineral structure to the coralline, and are called Melobesia or Nullipores. The sea-weeds are, as may have been gleaned from the last few pages, divisible into red, olive, or dark and green kinds, and one of their most interesting studies relates to the method of reproduction. Many sea-weeds are annual and die in the winter, so they must be reproduced by seed, or something like it; others are of two or more years’ growth, and outlive the winter, but in the end they must have some method of perpetuating their kind. Some are perennial, or constantly growing. Certain kinds are only found in the spring and summer, others are always to be met with, and some produce spores, or the matter out of which future weed grows, in summer, and others in the autumn and winter. The geographical range of some of the British sea-weeds is immense, and not a few kinds are found at the Antipodes. SARGASSUM --CUTHBERT COLLINGWOOD