As the forest must be planted before its denizens can luxuriate in its shades, so the submarine shrubbery of the Aquarium must be perfected before the aquatic animals can be introduced. For it has been shown, in tracing the history of the experiments which resulted in the establishment of the principles that regulate the formation of Aquaria, that it is by plants only that a supply of oxygen can be kept up, sufficient for the health and existence of all forms of animal life beneath the water.^[1] It is necessary, also, that the rays of sunlight should fall upon the foliage directly through the surface of the water; and when an Aquarium, with its plants, is placed in a position to receive the light in this manner, their fronds may be observed giving forth the gas in small silvery bubbles and corruscations, which have a brilliant and gem-like appearance.

Some marine plants appear to succeed much better than others, but I believe that happens only from their treatment being imperfectly understood; and I believe, not only that all the exquisitely beautiful marine Algæ of our own shores may be successfully grown, but also that the more splendid varieties of the tropical seas may be made to thrive in properly-heated Aquaria, and thus form one of the most attractive features of our hot-houses—one that has not yet been dreamed of.

In ordinary Aquaria, such as I am now treating of, I shall name first those species of sea-weed recommended by Mr. Gosse and others as most easily cultivated, but I shall also point out many other species, which I feel convinced may be successfully grown under proper management; and they certainly deserve every effort that can be made to establish them in Aquaria, as they are among the most beautiful of their tribe.

If not purchased of dealers, the plants must be very carefully collected by the amateur himself, taking care to detach a portion of the substance to which they are growing, and packing them in damp refuse sea-weed, keeping them out of their native element as short a time as possible.

The plants in most flourishing condition in the marine tanks of the Zoological Gardens, were at first those of the Chlorospermatous order, but others have since succeeded nearly as well. Plants of Ulva and Conferva have done very well, but the most successful growth has been that of a plant of the genus Bryopsis, which, entirely enveloping a large stone in its mossy and almost feather-like foliage, produces a very beautiful appearance. Those unlearned in scientific names will be glad, perhaps, to learn that these beautiful Algæ derive their title from two Greek words, Bryon (βρυον), a moss, and opsis (οψιϛ), a resemblance, from their likeness to some of the most delicate and feather-like mosses of our woods. The delineation of Bryopsis plumosa in Plate II., on the extreme left near the lower part of the Plate, will convey some idea of these elegant sea-weeds.

Chondrus crispus is a beautiful plant, and well suited to the Aquarium. It will often be found under ledges of rock, completely concealed by a pendant veil of Fucus, commonly known as the olive-weed; and, on lifting the tangled mass of its rank growth, many beautiful and unexpected plants are frequently found, but none strike the explorer more than the Chondrus. Its nacreous tints, like those of a pearl shell, varying wonderfully according to situation, being very remarkable. It is the Carrageen Moss of the herb market. This plant forms the principal object in the lower part of Plate IV., to the right.

Laurencia pinnatifolia is a pretty branching plant, also varying in hue according to the aspect in which it grows. In the shade it is purple, but when receiving the full influence of the sun’s rays, it assumes a light-yellow tone; just as the Lycopodium, known as Fortune’s Moss, is purple when grown in the darkest part of a room, but becomes of an ordinary green tone when placed for some time near the light. The Laurencia is shown at the upper part of Plate V., coloured pale-violet.

The splendid plant Rhodymenia palmata, with its finely-coloured, semi-transparent fronds, is also recommended. It is the Dulse, or Dellis, eaten by the inhabitants of our northern coasts as a delicacy. Another species of R. lacinata is represented to the left of Plate V., the transparent light-crimson fronds of which are excessively beautiful. Mr. Gosse tells us that the Rhodymenia palmata is not suited to an Aquarium, because it appears to require the motion of the sea, and soon begins to decay in still water. If that be the case, let us provide a remedy, for the plant is one of the most beautiful among all its lovely congeners. When a plant of the gigantic lily of the Amazon river was first introduced, it refused to flower in the tank provided for its northern home, at the Duke of Devonshire’s residence at Chatsworth. But Sir Joseph Paxton, who then directed the floricultural operations of that magnificent abode, was not discouraged; and, seeking to impart to the still water of the tank something of the motion of a deep and majestic river, he contrived that a small but continuous stream should enter at one end of the tank, and, as it entered, turn a small paddle-wheel, the action of which imparted a gentle, undulating motion to the water of the whole tank. The device was triumphant, and the glorious Victoria regia formed and expanded its giant flowers in the house which its curator had constructed for it, the plan of which eventually suggested the creation of the “Crystal Palace.” Let us not despair, therefore, of cultivating successfully the beautiful Rhodymenia palmata in our Aquaria. The construction of a suitable apparatus for imparting motion to the too still waters, will form a pleasant passetemps for some of our fair admirers of the pursuits of the Aquarium; and their success would be a signal triumph. But at present the beautiful red weeds, in general, are difficult of cultivation, and when they begin to exhibit spots of orange—a vegetable plague-spot not to be mistaken—it is a symptom of decay which should at once cause their removal from the Aquarium, before their decomposition leads to further mischief.

The common Coralline, Corallina officinalis, of which a small spray is represented in the extreme lower part of Plate V., near the centre, is the “arboret of jointed stone” alluded to by the poet, and is well suited to Aquaria, thriving with little trouble. The smaller and slenderer kind is also suitable; but care must be taken, in collecting, not to choose the detached white fragments, which are washed up with every tide, for they are only the skeletons of the plant. It is the rosy-tinted specimens, verging to violet and purple, and still attached to pieces of rock, that are alone fit to remove to the Aquarium.

The Cladophoræ are also stated to be very suitable, C. rupestris being a very useful plant for the purpose. It is of a bluish-green, that harmonizes well with the tone of the sea-water, and fills up little chasms in the artificial rocks with very good effect, especially in contrast with the reddish-purple tufts of Polysiphonia arceolata, which do well in an Aquarium, and are a great aid to the foliage of the little marine landscape. The elegant, fan-formed, and brightly-radiated Padina pavonia is likewise mentioned, and should at all events be tried, as the tufts of that graceful marine plant form very singular as well as beautiful objects in the tank.^[2]

I would also recommend the trial of all the plants delineated in the five Plates devoted to the sea-weeds in this little book.

In Plate I., the first, occupying the upper part, with leaf-like fronds of transparent crimson, is the beautiful and not uncommon sea-weed, Delesseria sanguinea. The delicate pale plant below, to the right, is Punctaria latifolia, thin as tissue-paper, and speckled over its pale-buff surface with bright but minute grains of black. To the left is a branch of Chordaria flagelliformis, the rich olive of which contrasts well with the red kinds of Algæ. In the front, growing on a detached pebble, is the Lichen-like Hildenbrandtia rubra, the rich carmine of which might be made to form an exquisite touch of colour, if tastefully placed in the Aquarium; and to the extreme right is a small tuft of Vaucheria submarina.

In Plate II., the principal object, near the top of the Plate, is a bush of Callithamnion arbuscula, which receives its name from the tree-like aspect which it assumes more distinctly than any other of the marine Algæ. Behind it, to the right, are the tall and graceful forms, with their crimped edges, of the slender Laminaria phyllitis. And below, still to the right, is a branch of Codium tomentosum, distinguished by its light, vivid green, and the edging of delicate ciliæ, which have the appearance of a border of paler green, to every branchlet. Still to the right, in the extreme foreground, is a broken piece of rock on which plants of the curious Leathesia Berkleyi have grown, like convex kernels of bronze. To the left are the red-violet tufts of the Bangia fusco-purpurea, and behind them, a branch of Bryopsis plumosa.

In Plate III. the bright-green feathery plant in the extreme background is Ectocarpus siliculosus; and behind it, the violet, antler-like fronds of Nemaleon multifida. The large, gracefully-bending frond of rich purple, with narrower and younger fronds springing from the same root, is Porphyra vulgaris, one of the commonest, but most splendid of our marine Algæ, with which, in combination with other plants of suitable contrast, the vegetation of the Aquarium may be rendered truly splendid, if it once be successfully cultivated; of which I have no doubt, when its natural wants are sufficiently studied and ingeniously supplied. The splendidly-marked plant to the right, with its black maculations and richly-frilled edge, is Nitophyllum punctatum, one of our most splendid species; and the curious pale-buff, tubular plant in front of it, is Asperococcus Turneri. Near the foot of the Nitophyllum is a little tuft of the delicate Dumontia filiformis; and, to the extreme left, a branch of the brown-fronded Rytiphæa pinastris, which receives its specific name from the somewhat Pine-like growth it frequently assumes. Immediately beneath it, on the extreme right, is a little cluster of Chordaria divaricata; and below, in the left foreground, are a few pink fronds of the curious Alga, Chrysemenia rosea; while, in the foreground, to the right, on a detached pebble, is a small mass of the pale-crimson Peyssonetia Dubyi.

In Plate IV. the principal object is a fasciculus of Taonia atomaria, rising behind the point of rock at the top of the Plate, behind which are two long fronds of the spotted Asperococcus; to the left is the horn-like Gigartina acicularis; and in the front, to the left, the crimson tufts of a pretty weed (Ceramium strictum), which our artist has made too like the Bangia fusco-purpurea.

In Plate V. the violet-toned Laurencia pinnatifolia is grouped behind the solid, deep-crimson fronds of Iridæa edulis, which are often perfectly Pear-shaped, like pieces of crimson leather neatly cut in that form; but the action of tides in rough weather often tears the edges, and wears holes through the texture of the plant, as shown in the principal frond. To the left is the bright-crimson Rhodymenia lacinata—one of our most exquisitely beautiful marine Algæ. The fronds are as thin as the finest conceivable tissue, and beautifully transparent, which is shown wherever the lacinations of the edge overlap each other, in which places the double thickness of the texture doubles, at the same time, the intensity of the colour, as indicated in the representation. On the same level, to the right, is a small group of the delicate green Ulva latissima—a plant which has proved useful beyond all others in Aquaria, as throwing off, under the action of the light, a much greater profusion of silvery globules of oxygen than any other species yet known. At the same level still, on the extreme right, is a sprig of the delicately-branched parasite, Polysphonia parasitica, growing on a small mass of pale sulphur-coloured Melobesia lichenoides, the Lichen-like Melobesia. To the extreme left, under the beautiful Rhodymenia, is a small branch of the bright, olive-tinted Ectocarpus tomentosus, looking much like a spray of wild Broom, and immediately below it, a few purple branchlets of Gracilaria confervoides; while in the left foreground lies a pebble, partly covered by a small plant of Zonaria parvula, from beneath which straggles a little branch of the common but pretty Coralline, the Corallina officinalis; and, to the right, a globe of the curious Codium bursa, of the French coast, which might easily be added to our native species in the Aquarium.

Such are a few of our beautiful coast Algæ, all of which I would advise the admirers of the beauties of the marine Aquarium to try; and if some refuse, in the present state of our knowledge of their habits and requirements, to make themselves happy in their pretty “crystal palace,” choosing rather to consider it a “prison of glass,” still a good number of them, I am persuaded, may be coaxed into displaying their beauties very genially within its transparent walls, which admit the bright sun rays as freely as the pale-green liquid glass which forms their native element.

The best time for making collections at the sea-side is a day or two after the full moon, when the tide recedes to its greatest extent, and parts of the shore become exposed, where some of the finest species grow, which cannot be conveniently approached at any other time. It must be borne in mind, also, that few of the floating pieces will grow, however fresh and seemingly washed off with their root. Certain success is only to be secured by chiselling off a portion of the substance on which the weed is growing—thus transplanting it with its own soil, as it were, about its roots, into the ocean garden of the Aquarium.