THE ANTIQUITY OF RIVER PLANTS
In the still gossamer weather of late October, when the webs lie sheeted on the flat green meadows and spools of the air-spiders' silk float over the waters, the birds and fish and insects and flowers of the best of England's rivers show themselves for the last time in that golden autumn sun, and make their bow to the audience before retiring for the year. All the living things become for a few brief hours happy and careless, drinking to the full the last drops of the mere joy of life before the advent of winter and rough weather. The bank flowers still show blossom among the seed-heads, and though the thick round rushes have turned to russet, the forget-me-not is still in flower; and though the water-lilies have all gone to the bottom again, and the swallows no longer skim over the surface, the river seems as rich in life as ever; and the birds and fish, unfrightened by the boat traffic, are tamer and more visible.
The things in the waters and growing out of the waters are very, very old. The mountains have been burnt with fire; lava grown solid has turned to earth again and grows vines; chalk was once sea-shells; but the clouds and the rivers have altered not their substance. Also, so far as this planet goes, many of the water plants are world-encircling, growing just as they do here in the rivers of Siberia, in China, in Canada, and almost up to the Arctic Circle. The creatures which lived on these prehistoric plants live on them now, and in exactly the same parts of the stream. The same shells lie next the banks in the shallows as lie next the bank of the prehistoric river of two million years ago whose bed is cut through at Hordwell Cliffs on the Solent. The same shells lie next them in the deeper water, and the sedges and rushes are as "prehistoric" as any plant can well be. In the clay at Hordwell, which was once the mud of the river, lie sedges, pressed and dried as if in the leaves of a book, almost exactly similar in colour, which is kept, and in shape, which is uninjured, to those which fringe the banks of the Thames to-day. These fresh-water plants show their hoary antiquity by the fashion of their generation. Most of them are mono-cotyledonous - with a single seed-lobe, like those of the early world. There is nothing quite as old among the Thames fishes as the mud fishes, the lineal descendants of the earliest of their race. But the same water creatures were feeding on the same plants perhaps when the Thames first flowed as a river.
The sedge fringe in the shallows, the "haunt of coot and tern" elsewhere, and of hosts of moorhens and dabchicks on the now protected river, is mainly composed of the giant rush, smooth and round, which the water-rats cut down and peel to eat the pith. These great rushes, sometimes ten feet high, die every year like the sickliest flowers, and break and are washed away. Few people have ever tried to reckon the number of kinds of sedges and reeds by the river, and it would be difficult to do so. There are forty-six kinds of sedge ( carex), or if the Scirpus tribe be added, sixty-one, found in our islands. They are not all water plants, for the sand-sedge with its creeping roots grows on the sandhills, and some of the rarest are found on mountain-tops. But the river sedges and grasses, with long creeping roots of the same kind, have played a great part in the making of flat meadows and in the reclamation of marshes, stopping the water-borne mud as the sand-sedge stops the blowing sand. They have done much in this way on the Upper Thames, though not on the lower reaches of the river. The "sweet sedge," so called - the smell is rather sickly to most tastes - is now found on the Thames near Dorchester, and between Kingston and Teddington among other places, though it was once thought only to flourish on the Norfolk and Fen rivers. It is not a sedge at all, but related to the common arum, and its flower, like the top joints of the little finger, represents the "lords and ladies" of the hedges. So the burr reed, among the prettiest of all the upright plants growing out of the water, is not a reed, but a reed mace. Its bright green stems and leaves, and spiky balls, are found in every suitable river from Berkshire to the Amur, and in North America almost to the Arctic Circle. In the same way the yellow water villarsia, which though formerly only common near Oxford, has greatly increased on the Thames until its yellow stars are found as low as the Cardinal's Well at Hampton Court, extends across the rivers of Europe and Asia as far as China. The cosmopolitan ways of these water plants are easily explained. They live almost outside competition. They have not to take their chance with every new comer, for ninety-nine out of a hundred stranger seeds are quietly drowned in the embosoming stream. The water itself keeps its temperature steadily, and only changes slowly and in no great degree, and then, when the plants are in their winter sleep the stream may well say that "men may come and men may go, but I go on for ever." The same is very largely true of the things which live in the brook.