The Cecropia seedbank (consisting of seeds of C. sciadophylla and C. obtusa) under pristine Surinam lowland rain forest was studied in 1970-1978. The germination of Cecropia seeds is strongly induced by normal daylight; Cecropia seeds also show a moderate germination in darkness with fluctuating temperature (20-30.degree. C). The Cecropia seedbank was sampled during a year at 2 mo. intervals to a soil depth of 2 cm. The average total number of viable Cecropia seeds in the humus and 0-2 cm layer amounts to 73/m2. The quantity of Cecropia seeds sharply decreases with depth, and most viable Cecropia seeds germinated from the 0-1 cm soil layer. Closed earthenware pots containing seeds of C. sciadophylla and C. obtusa were buried at 2 sites (in meso- and xerophytic forest) and the seeds periodically tested for variability. Seeds of C. sciadophylla as well as C. obtusa were highly viable after 62 and 48 mo. of storage, respectively, at the 2 sites. The results are discussed in relation to the natural germination conditions for Cecropia seed in the Surinam lowland rain forest. Possible germination trigger mechanisms for Cecropia seeds are normal daylight and fluctuating temperature. A review is given of the dispersal agents of Cecropia seed. Cecropia propagation is independent of specialized pollinators and dispersal agents; its opportunistic germination ecology enables the genus to exploit successfully natural openings and clearings in the rain forest.