The dynamics of a seed cohort over a one-year period and its laboratory germination requirements at eight constant temperatures in light and darkness were studied in Espeletia timotensis Cuatr., a giant rosette species from the Venezuelan Andes (paramo) at 4200 m elevation. After one year (coinciding with the end of the rainy season) 55 percent of the seeds remained viable, 17 percent had germinated, and mortality accounted for 30 percent. Soil samples collected at the beginning and the end of the rainy season and sieved to separate the buried seeds revealed naturally occurring viable seeds on both occasions. In the laboratory, maximum germination percentages were 80 and 67 percent in light and darkness, respectively, much higher than the germination percentage observed in the field. The adaptive significance of the asynchronous germination pattern in the seed bank of E. timotensis and the differences between field and laboratory germination are discussed. IN THE VENEZUELAN ANDES, paramo vegetation ranges from altitudes of 2800-4600 m where giant rosette plants of the genus Espeletia comprise a conspicuous physiognomic element. One of the dominant species in the highest paramo zone, Espeletia timotensis Cuatr., is a long-lived caulescent rosette growing to 3 m tall and restricted to well-drained slopes above 4000 m (Fig. 1). The frequent occurrence of night freezing temperatures throughout the year is a common feature in high tropical mountain environments (Hedberg 1964, Coe 1967, Troll 1968, Monasterio and Reyes 1980) and may limit germination and establishment (Smith 1980, 1981; Smith & Young 1982). For this reason and because it lacks vegetative propagation and reproduces polyannually (Monasterio 1983, Berry & Calvo 1987), we might expect adaptive characteristics in the timing and degree of germination synchrony of the E. timotensis seed bank. To date, very few studies have forcused on the seed biology of paramo species. Pannier (1969) found in E. schultzii, a widely distributed giant rosette, that germination percentages were higher in light and increased by drying and wetting cycles. Smith's (1975) studies of germination optima from altitudinal populations in five species showed that only seeds from high-elevation populations could germinate at temperature regimes other than that of their natural habitat. The objectives of this paper are to evaluate the dynamics of a seed cohort of E. timotensis over a one-year period and to characterize its germination requirements under laboratory conditions. Although the population dynamics and ecophysiological aspects in this species are fairly well known (Monasterio 1983; Goldstein et al. 1984, 1985; Rada et al. 1985), basic features of its seed biology have remained unstudied.