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Vallisneria (Mich.) L. Acquario Visita la collezione


" ...and he wants to honour me by giving the name Vallisneria to the plant dedicated to me... "


Pier Antonio Micheli, director of the Botanical Garden of Florence, in 1722 dedicated the genus Vallisneria to his friend, the Padovan naturalist Antonio Vallisneri, as is documented by a letter written by Vallisneri himself to a Florentine doctor in June of that year. .

Classification
The genus Vallisneria belongs to the family of Hydrocharitaceae ( Monocotyledon ) and includes about ten species of fresh, slow or stagnant water perennial sea plants found in temperate, tropical and subtropical zones of the two hemispheres. It includes the Vallisneria spiralis L. (the only one which grows in Europe), Vallisneria gigantea Graebner (South-East Asia, Australia) and Vallisneria americana Michaux (North-West America).


Morphology
The plants live under water and are anchored to the bottom by a short underground stem (rizoma). They have a rosette of ribbon-shaped, flaccid leaves which are finely serrated at the tip. They can be from a few decimetres long to over two metres, depending on the species and the depth of the water. The male and female flowers grow on separate plants (dioica). The male ones, which are small and numerous, grow in ovoid clusters supported by short, small stalks. The solitary female flowers have a small stalk which can be more or less twisted and which extends up to the surface of the water when the flowers bloom. Pollination takes place in summer: the male flowers detach themselves when they are mature, and float on the surface where, carried by the current, they encounter the female flowers. Once fertilization has taken place, the female stalk contracts into a spiral, dragging the flower towards the bottom where the fruit matures.

Conservation
Due to reclamation, canalisation and pollution, Vallisneria spiralis is becoming rarer and rarer in Italy. In the regional Red List of Italian plants (1997), it is considered under serious threat in Trentino, vulnerable in Lombardy, Friuli, Tuscany and Umbria and at less of a risk in Piedmont. Research on its presence in the Veneto is now underway.



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