Myriophyllum contributes some lovely members to the aquarium. All the plants of this genera are of elegant structure, the leaves finely divided and of a delicate emerald green. M. Spicatum is perhaps the best, but there are other species to be had of the dealers that are worthy of attention.
Potamogeton is an extensive genera of water-plants, numbering not less than fifteen species in the brooks and rivers of this country alone. P. fluitans, crispus, and densus, are most easily obtained, and they flourish in the tank, and make rich branching masses for the centre, or to climb over rockwork. They are all rather coarse and apt to shed their lower leaves, but, if well placed, produce a striking effect. They blossom freely in the aquarium, and that is a great recommendation.
MYRIOPHYLLUM SPICATUM.
Nuphar lutea is the best of the water-lilies for the purpose: it grows freely and produces graceful outlines below and above. It should be planted early in spring to secure blossom; but if it does not throw up blossoms in summer it may be removed, and its place supplied by a plant in full bloom. Nymphæa macrantha and Nodorata minor are also highly suitable.
Ericaulon, or the pipewort, sends its only English species—E. septangulare—to the tank. It is a bog plant, rises six inches high, and does not succeed if immersed more than three inches; hence it is suitable for the top of an arch, but not for the deep water of the tank. The plant is perennial and produces a white blossom, with one petal and four stamens. The flower-stem is velvety, and the leaves spread in a tuft from the root.
POTAMOGETON DENSUS.
Utricularia Vulgaris, or the hooded milfoil, may be recommended as a botanical curiosity, but is met with only (as far I know) in the brooks of the southern counties—Hants and Surrey especially. It produces a yellow blossom in June and July. The root has a curious inflated appendage. There are two other species, U. minor and U. intermedia, differing but little in general aspect from the common sort.