The genus Echinodorus
This genus is part of the family Alismataceae. The family is named after Alisma plantago-aquatica, an European swampplant.
The family Alismataceae consists of 11 genera with about 80 species. All species are aquatic or semi-aquatic herbs and grow as hydrophytes or
amphiphytes. For aquaristic use are only two generas of interest: The genus Sagittaria with approximately 25 species and the genus Echinodorus with
presently 28 species. Whereas Sagittaria occurs in temperate and tropical regions all over the world, Echinodorus is restricted to the American
Continent. The distribution ranges from the northern United States of America to Argentina and Chile.
All taxons of Echinodorus are growing as amphiphytes or hydrophytes in freshwater. The non chlorophyllous stems are rhizomatous. The rhizome
tissue is usually uniform and contains starch. The roots are adventitious, arising from the stem. The leaves are aranged in a basal rosette. Normally
they have long petioles, but they can also be without visible petioles. The blade can have linear, lanceolate, or even round forms. They can be cordate
or acute angeled to the petiole. In good conditions the plants give rise to inflorescences, with one ore more pseudowhorls. The pseudowhorls are
separated by internodes and have usually three bracts where flowers ore side branches appear. Characteristic feature for Echinodorus are perfect flowers
with male and female parts. There are allways 3 petals and 3 sepals. The fruits are small nutlets, which are arranged as composed fruits looking like an hedgehog. Tis is the reason for the name Echinodorus.
The genus Echinodorus is a phyllogenetically young genus. There are often only slight differences between the species. There are floating transitions
between related species. You can detect often ecoligical races as well as wild crossbreeding. The extraordinary polimorphology complicates the determination of new taxons to existing species.
In the last 20 years nurseris crossbreeded many species and the aquarist community got a lot of new hybrids. They are often sold under scientific
apearing names, but are confusing to both scientists and hobbyists.
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