When a garden is so situated that it can be supplied with living or running water, a collection of aquatic plants in an aquarium, in connection with a fish pond, will be an object of additional interest to the pleasure ground. But on no account would I advise an appendage of this sort to a garden, unless it be fed by a stream of water or spring. A dug-out, even if water can be obtained the year round, without an outlet or inlet, is a great nuisance, and only fit for raising frogs, musquitoes, and for the growth of green confervae upon its stagnant surface. With a stream or never failing spring of water, an aquarium can be made without much expense, if not on too large a scale. It should be at least three feet deep, and lined with a substantial stone wall; it should have a margin of grass, or be edged with rough or dressed granite or free-stone, surrounded with a nice gravel walk. The portion of aquarium designed for most plants, should be three feet deep, in addition to a good depth of rich soil, while the bottom of the other section should be laid over with small pebbles, that the fish may be more distinctly seen; a few large shells will add to the interest of the pond. The most interesting aquatic plant of our country is the well known and universal favorite, the Nymphaea odorata, the Water Lily. Its botanical name signifies "the Nymph or Naiad of the Streams." Few plants possess more exquisite fragrance than the common Water Lily. When floating upon the surface of the water, its open petals spread out to receive the genial rays of the sun; it is an object of great interest, and may be truly considered the embodiment of purity and loveliness. It is generally found in deep water, where its roots are secured from the frosts in the winter by a sort of natural hot-bed being thus provided for it. In my experience, two feet of water is amply sufficient to protect it. The roots creep through the muddy bottom of ponds to a great extent. They are very rough, knotted, blackish, and as large as a man's arm, and difficult to extract from the bottom of deep water, but when taken up there is no more trouble. Tie stones to the roots, and throw them in to the part of the pond prepared for them, and they will soon establish themselves. There appears to be two common varieties, one with stout green stems, green calyx and white within, and the petals without any tint of pink or purple; the other has brown stems, more slender; flowers with brownish green calyx and pinkish white within, the outer petals tinged with red on the under side. While I resided in Lancaster, Mass., I found a beautiful variety, in a corner of a pond in that town, with pink petals, which I transferred to a small pond in my garden, where it flourished until I left the place. The pond was afterward drained, and I suppose the root was destroyed. Mr. Mr. E. Carter, formerly of the Botanic Garden, Cambridge, procured from the same pond a root which flourished many years in the aquarium there, but in clearing it out by one of his successors, I understand this rare variety was destroyed. I fear that no more of it can be obtained, as there was but one spot in the pond where it was found, and I thought at the time that Mr. Carter and myself took possession of all the roots.
N. odorata minor, is a rare variety with very small flowers and leaves, which I have found in some ponds, but cannot remember where. These varieties of the white lily will be sufficient for a small aquarium - but if it be of larger dimensions, there are a number of other species of native aquatic plants, which may be introduced.
Nuphar advena, or Yellow Water-Lily, has roots similar to N odorata; it has a very curious flower, but the odor of it is the opposite of that flower, for the smell is anything but agreeable.
Pontederia cordata, or Pickerel-weed, is found in shallow water; its tall spikes of blue flowers are quite ornamental. For this plant the soil should be raised to within one foot, or foot and' a half, of the surface of the water.
Sagittaria Sagittifolia, is a handsome plant found about the margin of ponds and brooks in shallow water. Its white flowers arranged in whorls of three, are produced in July and August; the depth of water over these roots need not be more than 3 or 4 inches. A portion of the soil on the margin may be raised a few inches above the water level, which will be a suitable place for the beautiful Lobelia cardinalis, of our meadows, for the curious Sarracenia or side-saddle flower, and for many other bog or swamp plants.