Aquatic plant

“ Although there is such a contrast in the degree of uniformity of their life-conditions between land and water plants, a strictly aquatic plant being but slightly affected by changes in the physical conditions that are accompanied by a complete transformation in the character of the terrestrial vegetation, yet—and this is the important point—we find the same principle of differentiation at work with both land and water plants. ”

“ Selection of Plants.—There is scarcely any aquatic plant but may be grown in an aquarium, and unless some attention is given to the botanical department, only half the pleasure and instruction it is capable of affording is attained. I cannot agree with Mr. Gosse, that the vegetation of a tank has so strictly a secondary place—"preserved because they cannot be dispensed with,"—for in either a marine or fresh-water vessel the vegetation is a special source of beauty and interest, and fairly divides attention with the animals. ”

“ The great majority of water plants send their flowers up above the surface to be pollinated by wind or (more rarely) by insects. It may be noted that few of the more highly evolved groups of Seed{201} Plants are represented in the aquatic flora; wind-pollinated flowers of a rather primitive type of structure are the rule in our lakes and rivers; which points to an early assumption of the aquatic habit, and suggests that the land is more favourable than the water for the evolution of higher types. ”

“ Whilst the beach and the river in most cases possess plants that have very wide ranges over the earth, a good proportion of the species on the mountain-summit are not found elsewhere. This implies a partial suspension of the means of dispersal on the mountain-top, whilst the currents and waterfowl are still actively distributing the seeds of the littoral tree and of the aquatic plant. ”

“ SOIL FOR GROWING AQUATIC PLANTS.
The best soil for growing aquatics, is that obtained from the bed of a pond, or a slow, swampy stream, but when this is not readily obtainable, a mixture of equal parts of good, rich garden loam and stable manure will be almost as good. Some use a mixture of muck and bog peat, from which they claim very satisfactory results in growing aquatics; either we think can be used with good success. ”

“ So, too, is the marvellous arrangement of the water-plants, which fall gracefully into the scheme of decoration. All is still in the deep water, but on the shoulders are the water-lilies, and above them are the waves seemingly agitated by the rough wind. To recapitulate and to give the colours we specially call attention to this fine pair of square taper-shaped vases which are in all probability unique as a pair, decorated with fishes and aquatic plants in aubergine, green, yellow, black, and white, on a pale apple-green ground; the edges and borderings of yellow enamel. ”

“ The perspiration of aquatic plants seems to be remarkably copious. Of these some grow constantly immersed in the water, as most species of Potamogeton, Pond-weed, Engl. Bot. t., 297, 376, &c. Their leaves are peculiarly vascular, and dry very quickly in the air, withering in a very few minutes after exposure to it. Their absorbing power seems equally great, so that they appear to be continually, in their natural situation, imbibing and giving out a quantity of water much greater than has been observed in land plants. ”

“ On the shores of one of these pools, of size not so great that the waves may attain a considerable height, or in the sheltered bay of a larger lake, various aquatic plants, especially the species of pond lilies, take root upon the bottom, and spread their expanded leaves on the surface of the water. These flexible-leaved and elastic-stemmed plants can endure waves which attain no more than a foot or two of height, and by the friction which they afford make the swash on the shore very slight. ”

“ It necessitates frequent changing of the water for at least a fortnight after the first stocking of the tank, in order to get rid of the soluble vegetable matter, which the water dissolves out of it, and its presence promotes the growth of confervæ, and other low forms of aquatic vegetation, that become obnoxious to the sight, and even hurtful to the health of the collection. I now use sand and pebbles only, and I find that aquatic plants of all kinds root freely and flourish in it, and, indeed, if pebbles only be used, they flourish just as well if their roots are covered. ”

“ These squares are again divided into beds for the herbaceous plants, wherein a good collection are cultivated. In one of the divisions there is an aquarium for aquatic plants, which consists of oblong square troughs, lined with brickwork for retaining the water; these are about two feet wide by two deep, and an intervening space of ground, of from six to eight feet, in which are grown such species as do not require the water: but a damp situation, notwithstanding, is requisite: In the apartments where the hardy perennial plants are cultivated, are numerous apple trees, all in full bearing ”

“ On the sea-coast I found also several plants, whose characters similar to others I already knew, enabled me to recognize pretty well their properties. They are all alike, fat and strong-full of sap and clammy,—and it is evident that the old salt of the sandy soil, but still more the saline atmosphere, gives them these properties. Like aquatic plants they abound in sap, and are fleshy and tough, like mountainous ones; those whose leaves shew a tendency to put forth prickles, after the manner of thistles, have them extremely sharp and strong. ”

“ There are as many materials and methods for building pools as there are sizes and shapes. The depth depends on the requirements of the aquatic plants to be grown, and so does the location in sun or shade. Pygmy water lilies, for example, need all available sun, and at least ten inches of water—four inches for the container that holds soil and roots, eight inches above the crowns or growing points. Other miniature water plants are satisfied with much less. ”

“ Their culture in tubs, casks, or fountains on the lawn, is so very simple a matter, and the flowers bloom so freely, every garden should have a corner for aquatic plants. Secure the water-lily roots as early in the spring as possible, and barely cover them with good rich loam or muck spread over the bottom of the sunken tub to a depth of six or eight inches. After it has been filled with water, and replenished from time to time to make good the loss by evaporation, the water garden needs no attention until autumn. ”

“ The submersed aquatic has many or all of its cells in direct contact with the water. The land plant has only those cells which touch, or are in, the soil which are regularly in direct contact with water. Except those plants living in swamp or marsh, and except immediately after heavy rain, land plants are able to obtain only those thin films of water held on the surfaces of the soil particles. ”

“ The pressure of competition has probably driven them into the water, where they descend as far as the lessening light-supply will allow. Some—presumably the earliest to take to an aquatic life—have all their relations to keep them company, the remote ancestor which adopted an aquatic habit being now represented by many species, or even by many genera. In other cases a terrestrial genus or order has few or only a single aquatic representative. ”

“ The seeds are often barren; and the only mode is to plant the shoots or strings in drills at nine inches apart, laying them lengthways along the drills, the ends of one touching the other.
6. AIRA aquatica. WATER HAIR-GRASS.—This is an aquatic, and very much relished by cattle, but cannot be propagated for fodder. Water-fowl are very fond of the young sweet shoots, as also of the seeds; it may therefore be introduced into decoys and other places with good effect. Pulling up the plants and throwing them into the water with a weight tied to them, is the best mode of introducing it. ”

“ The aquatic plants growing on the bed of this portion of the lake are, when living, all specifically lighter than water, which may easily be proved by detaching any of them from the bottom, when they will be found to rise to the surface. ”

“ In the cavities between the stones, filled with earth, alpine or trailing plants are inserted, and also some of the choicest flowers. In proper situations, a small pool of water may be introduced for the culture of aquatic plants. In these days the rock-garden is a most important feature, and it requires a good deal of care and skill to arrange the boulders, walks, pools or streams in natural and artistic fashion. The selection of suitable alpines, perennials and shrubs and trees also necessitates considerable knowledge on the part of the gardener. ”

“ Such [3] differences would seem to give us a kind of division into classes, for instance, between that of aquatic plants and that of plants of the dry land, corresponding to the division which we make in the case of animals. For there are some plants which cannot live except in wet; and again these are distinguished from one another by their fondness for different kinds of wetness; so that some grow in marshes, others in lakes, others in rivers, others even in the sea, smaller ones in our own sea, larger ones in the Red Sea. ”

“ The plants render the water fit for the maintenance of animal life, while the animals check the too rapid increase of vegetation. Thus, the success of our aquarium will depend upon the proper balance of animal and vegetable life. We select the green and red weeds, as the brown and olive are apt to discolour the water. Sea-plants have no roots, but adhere by minute discs to the surface of the rock; a piece of stone has accordingly to be knocked off with each plant, in order that it may be removed to our glass tank. ”

“ Seaweeds and their like, which propagate by a kind of spores, may remain below the surface for ever; but flowering plants for the most part must come up to the open air to blossom. The sea-weeds are in the same position as fish, originally developed in the water and wholly adapted to it, whereas flowering plants are rather analogous to seals and whales, air-breathing creatures, whose ancestors lived on land, and who can themselves manage an aquatic existence only by frequent visits to the surface. ”

“ It is better to have too few plants or animals than too many of either. A great deal of light, especially bright sunlight, is not good for the aquarium. A pond that is not shaded soon becomes green with a thick growth of slime or algæ. This does not look well in an aquarium and is likely to take up so much of the plant-food that the other plants are "starved out." The plants in the school-room window may provide shade for the aquarium, just as the trees and shrubs on its banks shade the pond. ”

“ The name literally means water-plants. The water conditions in which such plants grow range from complete submergence to swamps. Such plants have various adaptations for living in connection with a large amount of water. If the plant lives submerged, there is a feeble development of the tissues for mechanical support, and when it is removed from the water it collapses. Another common adaptation of water-plants, found also in swamp forms, is the development of conspicuous air-passages for aeration. ”

“ By following up the clue supplied by the floating seed, we have arrived at the conclusion with respect to the British flora that plants with buoyant seeds or fruits gather at the water-side. But we have yet to inquire why some of these plants are “located” at the sea-coast and others on the borders of ponds and rivers. Mere buoyancy aided by chance has not determined the choice. There are definite principles at work in the economy of plant-life that make the selection for each plant. ”

“ For the purposes of aëration we have to rely principally on the bright green weeds, and preference should be given to any of these that exhibit, in their natural habitat, a multitude of minute air-bubbles on the surface of their fronds, for the bubbles consist principally of oxygen that is being liberated by the plant, and denote that the species in question are those that are most valuable for maintaining the desired condition of the water in an aquarium. ”

“ A FRESH WATER AQUARIUM. BY A. W. ROBERTS.
Many fresh-water plants have a tendency to grow above the surface. When this takes place, the leaves become so different in shape that they can hardly be recognized as belonging to the same plant. Therefore care must be taken to keep all plants submerged that are intended to supply air for the fish.
MERMAID-WEED.
One of the most common plants is the mermaid-weed (Proserpinaca) . I have drawn it submerged and out of water, to show the change in the leaf. It grows along the margins of ponds that partially dry up in summer. ”

“ Other bouga extend out from the Lake up to forty miles, and are known by aquatic vegetation, such as lotus, papyrus, arums, rushes of different species, and many kinds of purely aquatic subaqueous plants which send up their flowers only to fructify in the sun, and then sink to ripen one bunch after another. Others, with great cabbage-looking leaves, seem to remain always at the bottom. The young of fish swarm, and bob in and out from the leaves. A species of soft moss grows on most plants, and seems to be good fodder for fishes, fitted by hooked or turned-up noses to guide it into their maws. ”