Abstract
The paper briefly outlines work being done on the movement of cations under a Palmetum-type rain forest near Manaus, Amazonas. It is suggested that the low cation content of river waters Is concerned with the nature and dynamics of water movement in relation to soil moisture and tension as much as lack of availability of cations in the soil. Preliminary results support the idea of a 'by-pass' mechanism whereby the smaller pore spaces, saturated with water, only drain and provide cation-rich water late in the dry season.