Water-thyme (Anacharis canadensus) grows in slow-flowing streams. It requires coaxing to establish it in an aquarium, but when once rooted, is apt to grow too fast, requiring thinning out. Heap plenty of gravel on the root ends. Do not tie the bunch with string, as it will cause it to decay.
NITELLA.
Nitella flexis is almost a rootless plant, and will grow without any care. It is found growing in shady parts of cool ponds, streams, and lakes.
FONTINALIS.
Fontinalis antipyretica grows in springs and cool, shady ponds. It resembles a very fine and long moss. In color it is of a beautiful light green. I have often stored up quantities of this plant during summer (it becoming perfectly dry), that I might have it for winter use, and when placed in an aquarium it started out as fresh as ever.
DUCK-WEED.
Duck-weed, or duck's-meat, is a small floating plant, covering the surfaces of ponds and lakes in shady places. It is one of the best surface plants for producing shade, or for cutting off light that enters from the top of the water. Its thousands of rootlets afford hiding-places for numerous small aquatic animals, such as the hydra, crimson water-spider, and the brick-maker.