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.
Many of the flowers are not quite what their names imply. The true lilies are among the oldest of plants. But "water-lilies" are not lilies. They have been placed in order between the barberry and the poppy, because the seed-head of a water-lily is like the poppy fruit. The villarsia, which looks like a water-lily, is not related at all, while the buck-bean is not a bean, but akin to the gentians. Water-violet might be more properly called water-primrose, for it is closely related to the primrose, though its colour is certainly violet, and not pale yellow. By this time all the bladderworts have disappeared under water. In June in a pool near the inflow of the Thames at Day's Lock, opposite Dorchester, the fine leafless yellow spikes of flower were standing out of the water like orchids, while the bladders with their trapdoors were employed in catching and devouring small tadpoles. There is something quietly horrible about these carnivorous plants. Their bladders are far too small to take one in whole, but catch the unhappy infant tadpoles by their tails and hold them till they die from exhaustion.
The bank flora of the Thames is nearly all the same from Oxford to Hampton Court, made up of some score of very fine and striking flowers that grow from foot to crest on the wall of light marl that forms the bank. Constantly refreshed by the adjacent water, they flower and seed, seed and flower, and are haunted by bees and butterflies till the November frosts. The most decorative of all are the spikes of purple loose-strife. In autumn when most of the flowers are dead the tip of the leaf at the heads of the spikes turns as crimson as a flower. The other red flowers are the valerian, in masses of squashed strawberry, and the fig-wort, tall, square-stemmed, and set with small carmine knots of flower. In autumn these become brown seed crockets, and are most decorative. The fourth tall flower is the flea-bane, and the fifth the great willow-herb. The lesser plants are the small willow-herbs, whose late blossoms are almost carmine, the water-mints, with mauve-grey flowers, and the comfrey, both purple and white. The dewberry, a blue-coloured more luscious bramble fruit, and tiny wild roses, grow on the marl-face also. At its foot are the two most beautiful flowers, though not the most effective, the small yellow snapdragon, or toad-flax, and the forget-me-not. This blue of the forget-me-nots is as peculiar as it is beautiful. It is not a common blue by any means, any more than the azure of the chalk-blue butterflies is common among other insects. Colour is a very constant feature in certain groups of flowers. One of these includes the forget-me-nots, the borage, the alkanet, and the viper's bugloss, which keep up this blue as a family heirloom. Others of the tribe, like the comfrey, have it not, but those which possess it keep it pure.
The willows at this time are ready to shed their leaves at the slightest touch of frost. Yet these leaves are covered with the warts made by the saw-flies to deposit their eggs in. The male saw-fly of this species and some others is scarcely ever seen, though the female is so common. The creature stings the leaf, dropping into the wound a portion of formic acid, and then lays its egg. The stung leaf swells, and makes the protecting gall. It is difficult to say when "fly," in the fisherman's use of the term as the adult insect food of fish, may not appear on the water. Moths are out on snowy nights, as every collector knows, and on any mild winter day flies and gnats are seen by streams. In the warm, sunny days of late September, numbers of some species of ephemerae were seen on the sedges and willows, with black bodies and gauzy wings, which the dace and bleak were swallowing eagerly, in quite summer fashion. The water is now unusually clear, and as the fish come to sun themselves in the shallows every shoal can be seen.
Among the typical Thames-valley flowers, all of which would be the better for protection, are the very rare soldier orchis (Orchis Militaris) and the monkey orchis (Orchis Simia), the water-snowflake, thehottonia, or water-violet, the water-villarsia, more elegant even than the water-lilies, the flowering rush, with a crown of bright rose-pink flowers. The two orchids named are very interesting plants. Of the monkey orchis Mr. Claridge Druce says in his "Flora of Oxfordshire" that it has become exceedingly scarce, not so much from the depredations of collectors, but from the fondness of rabbits for it and the changes brought about by agriculture. The soldier orchis is very rare indeed; both are only found in a few woods in the Thames valley, and possibly in Kent. The bladderworts fade instantly, and are not much interfered with, and though the fritillaries are picked for market, the roots are not dug up because that would injure the meadow turf in which they grow, and business objections would be raised.