Oxygenating Plants
The following plants are suitable for either the aquarium or the pond, with the exception of Anacharis which may spread to such an extent as to choke an the other plants. Some of the oxygenating plants are sent out in a bundle and may have no roots; if they are intended for the pond, the
bundle should be weighted with a piece of lead or a pebble and lowered into the water at the required spot. For the aquarium, the individual stems should be weighted and laid on the sand, but not placed in the sand, otherwise the stem win rot.
Callitriche (Star Wort) (plate ii).
Ceratophyllum (Horn Wort) (plate ii). Chara (plate ii).
Elodea caUitrichoides, E. crispa, E. densa (plate ii), and, of course, E. canadensis, otherwise Anacharis or Water Thyme. The last-named does not flower in this country usually.
Eriocaulon (Pipe Wort) (plate u). Ludwigia (LoosestriIe) (plate iii). Myriophyllum (Water Milfoil) (plate iii). Potarnogeton (plate uu).
Ranunculus aquatilis (Water Crowfoot) (plate ii). Utricularia (plate nu). VaUisneria (Tape Grass) (plate iii).
Myriophyllum and Vallisneria are perhaps the best plants for the pond, they are good oxygenators and do not spread too rapidly, moreover the dense foliage of the former is ideal for the fishes when depositing their eggs.
The above plants are notable rather for the mass of greenery they produce, than for their flowers, there are, however, other oxygenating plants that bear delightful flowers. Hottonia palustris or Water Violet (plate iv) has a profusion of pale mauve flowers that stand some nine inches above the water. The Water Lobelia, Lobelia Dortmanna (plate iv), has short thick leaves from the centre of which rises a long thin stem bearing dainty pale-blue flowers. The two plants just mentioned are ideal for the shallow pool or the margin of the larger pond.
Finally, there are the Sagittaria species, ten at least are cultivated in this country, perhaps the most popular oxygenating plants for pond, lake or aquarium. The arrowhead-shaped leaves, standing as they do well out of the water, relieve any flatness and greatly improve the general effect. The most popular species for pond cultivation is the Common Arrowhead (Sagittaria sagittifolia) (plate iv) which should be planted in a foot of water, the leaves standing out of the water some eighteen inches. The aquarium species pusilla, natans and brevirostris have the fohage entirely submerged, with the flowers just rising above the surface.