The research was carried out in a representative area of the semi-arid Sicilian inland; its aim was to study the evolution of the reproductive process in Medicago arborea in open pollinated and in caged conditions. On the basis of two groups of 4 plants each, eight years old and, with a 4 x 4 layout of planting, 4 reference units were selected for each plant; as the first raceme appeared, on each reference unit every two weeks until maturity the number of racemes, of flowers and of pods/raceme were observed, as also the number of seeds/pod at ripening. The results pointed out: - the plants in open pollinated conditions produced on the whole meanly 80000 flowers with a growing formation trend until the maximum value (1800 flowers/d) was reached during the third decade of April; moreover a mean fertility of 33 per cent was observed (similar to that of some herbaceous legumes in the same area). - In caged conditions the flowering period was 25 days longer, flower production higher by 40000 flowers, and a mean selfing quota of 6 per cent was observed; height and diameter were also greater than in open pollinated conditions.