ABSTRACT
There are several well-known associations that occur between mosses, liverworts, and ferns that grow on metal-enriched substrates. These groups of plants each possess certain anatomical and physiological properties that enable some repre sentatives to occupy unique ecological niches in natural and man-made metaliferous environments. The best documented of these are the groups of specialized bryophytes that are found on substrates enriched with copper; so-called copper mosses are found worldwide (1) and come from widely separated taxonomic groups. Other bryophytes are associated with lead-and zinc-enriched substrates. Serpentine soils do not appear to possess a distinctive bryophyte flora. Some species of pteridophytes are associated with serpentine substrates in various parts of the world (2-4), while several African species grow on copper-enriched soils or on soils polluted by metal smelter emissions (5). The existence of these diverse groups is a clear indication of the ability of Bryophytes and Pteridophytes to adapt to extremes of metal content of their growth substrate, either by avoiding
the toxic constituents or by expressing resistance/tolerance to metals at an organismal or cellular level.
