The aqua cardener

摘要

There are three common freshwater species of Vallisneria -- spiralis (Straight Vallis), gigantea (Giant Vallis), and asiatica var. biwaensis (Corkscrew Vallis). All these plants belong to the Hydrocharitaceae or frog-bit family. The word Hydrocharitaceae comes from the Greek words hydro meaning water and charis meaning elegance, most of the members being showy aquatic plants. V. spiralis grows in the mud at the bottom of fresh-water streams and ponds in tropical and sub-tropical regions. It is verycommon in Southern Europe, and temperate North America. The name spiralis applies to the shape of the flower stems, however, it is also known as eel grass or tape grass. This species requires deep water, as the leaves are long and it is necessary to cover them. They are light green and lined, and are good oxygenators in tanks. The roots are fibrous and help to purify the soil; propagation is by horizontal runners, on the end of which the new plants form. These new plants are the same sex as the parentplant -- the majority of them being female. Few of the seeds germinate successfully, but when they do, they produce both sexes.