Water lilies (Nymphaea) can be used to restore the purity of rivers and water sources polluted with poisonous heavy metals, and to treat waste water originating from household or industrial sources. Experiments carried out at the Hebrew Univesity, Jerusalem, Israel, have shown that the watet lity, generally thought of only as a decorative plant, is capable of absorbing huge quantities of heavy, poisonous metals through its leaves and roots.