The binding of REE with water-soluble polysaccharides (PSs) in leaves of fern Dicranopteris Dichotoma (DD) has been studied by molecular activation analysis.The cold-water-soluble and hot-water-soluble PSs in leaves of DD were obtained by using biochemical separation techniques. The PSs of non-deproteinization and deproteinization

were separated on Sephadex G-200 gel permeation chromatography.The absorption curves of elution for the PSs were obtained by colorimetry

and the proteins were detected using Coomassic brilliant G-250. Eight REEs (La

Ce

Nd

Sm

Eu

Tb

Yb and Lu) in these PSs were determined by instrumental neutron activation analysis. The results obtained show that the REEs are bound firmly with the water-soluble PSs in the plant. A measurement demonstrates that the PSs bound with REEs are mainly of smaller molecular weight (10

000 to 20

000 Dalton).