Experiments described suggest that formation of polyphosphate, found previously in Banksia ornata, occurs also in five other Australian heath species: Banksia serrata (Proteaceae), Hakea ulicina (Proteaceae), Casuarina pusilla (Casuarinaceae), Hypolaena fastigiata (Restionaceae), and Lepidosperma concavum (Cyperaceae). As these species belong to highly evolved angiosperm families, polyphosphate synthesis is not restricted to "primitive organisms" as suggested by earlier workers. It is suggested that, since environmental stress conditions are necessary for polyphosphate synthesis in microorganisms, this is also the case for higher plants, and that these unusual conditions may be a natural factor of the oligotrophic heath environment. Indications of polyphosphate synthesis have not been demonstrated in Pinus radiata, a forest tree often planted on the same soils as those which support the above heath species.