Twelve experimental populations were obtained by making monthly so wings in 3 cm deep de pressions spaced one meter a part in 5,00 x 3,80 m plots. After 20 days the plots were thinned to leave 120 plants 20 cm apart. Each month 10 plant s were randomly harvested and the reproductive structures counted. Four sowing periods wer e distinguishab le based on the number of racemes, fascicles and ca ryopse s produced , the time of initiation of flowering, duration of fascicle dispersal and life cycle length. The first period includes so wings made in the months of november to january and is characterized by the highest production of racemes and fascicles, about 70% of the total, as well as the greatest production of caryopses. Also, the initiation of flowering was th e most precocious (2 nd month), the period of fascicle dispersal the longest (210 days), the dispersal index the highest (72%) and the life cycle long (210 days). The second period includ es sowings made in Februa ry and March and is characterized by the lowest production of racemes, fas cicles and caryopses (2% of the total) . Initiation of flowering was late (4 th month) . Fascicle dispersal ocurred during 60 days and the dispersal index was the lowest observed (44%). Life cycle length was 180 and 150 da ys re spectively fo r the January and February sowings. The third period includes April to June and was characterized by low raceme production (19% of the total) and intermediate production of fa sc ic le s an d ca ryopse s (about 21% of the total). The initiation of flowering was retarded (4th month), fascicle dispersal lasted 60 days for the April sowing and 90 days for the sowings of May, June and July. The dispersal index was 70% and life cycle length was 210 days. The fourth period, sowings of August and October, was characterized by very low production of racemes, fascicles and caryopses (7% of the total). Flowering was initiation in the third month and fascicle dispersal ocurred during 60 days. The dispersal index was 47% and life cycle length 150 (August sowing) and 120 (September and October sowings) days.
sandbur; life cycle; reproductives; structures; dispersion