Vallisneria americana
USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. Vol. 1: 106. - Foto visualizzata 255 volte

Vallisneria spiralis
Hippolyte Coste - Flore descriptive et illustrée de la France, de la Corse et des contrées limitrophes, 1901-1906 - This image is in public domain because its copyright has expired. - Foto visualizzata 544 volte