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Size class distribution is important in understanding population structure, demography and stability of populations. In this study, the size structures of two semi-desert under-shrub populations, soil characteristics of habitats, spatial pattern of plant populations and reproductive capacity of the populations of two plant species i.e., Senna holoceracea and Fagonia indica were examined in two different sites. Size class distribution of both species were positively skewed, having greater frequencies in the smaller classes that represents adequate recruitment. This shows adequate recruitment in the populations of both the species. The examination of spatial pattern, using sample plot and plotless methods, disclosed aggregated pattern of both the species populations. Soil characteristics were also found spatially variable, showing higher fertility (organic matter, nitrogen, Ca, Mg and K) underneath the selected plants and lower in the gaps, which is one of the principal cause of aggregation in species populations. Fecundity of the two plants were also found to be different, particularly differences were found in the fecundity of same plant at the two sites which was presumably due to difference in plant size.