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a plant with an extremely deep root system that uses groundwater as its source of moisture. A classical example is the date palm (Phoenix dactylifera), which grows on oases in the Sahara and the Arabian Peninsula. (An ancient Arabic proverb says that the date palm has its head in fire and its feet in water.) Phreatophytes occur in the subtropical eucalyptus forests on the eastern coast of Australia. They serve as indicators of the depth and salinity of the groundwater. For example, the licorice (Glycyrrhiza glabra) is an indicator of fresh water at depths of 5 to 10 m, and Halostachys caspica indicates salt water at depths of 5 to 15 m. Typical phreatophytes include many desert and semidesert plants, for example, camelthorn (Alhagi camelorum), tamarisk (Tamarix), and Achnatherum.