Thanks to a marking method in natural conditions, which is described, a demographic analysis is made in Ouango-Fitini savannas (401 W, 935 N) for the leaves populations of four Grasses species. The provided data are: survival curves and life
expectancies of the leaves cohorts in relation to their period of emergence, fluctuations in the number of leaves, in the age-structure and in the natality and mortality of the populations.