Among ferns, data indicate aluminum accumulation in several species of Filicales and in some species of Cyatheaceae. Among Lycopodiales, scanty data indicate little or no accumulation except in Eulycopodium, in which there is a rise in aluminum content with increasing morphological complexity. Among thallophyta and bacteria, the aluminum content of marine algae is relatively low while accumulation of it is suggested in fungi. Physiological and ecological aspects of aluminum in plants, and possible biological functions in normal and pathological metabolism are discussed.