the intertropical zone. This comprises the equatorial latitudes, the tropics and subtropics. It is not only that part of the globe lying between latitudes 30° north and south of the Equator, as proposed by some writers (DAVIES, W., 1960; repeated by DAVIES & SKIDMORE, 1966). Rather is it those regions of the world in which, at the lower elevations, certain families and members of the Gramineae and Leguminosae grow wild or can be cultivated. It may be a matter for discussion whether these plants in their wild communities or sown or planted crop mixtures are better indicators of a biological environment than the instruments and criteria of the meteorologists.