The seed surface morphology of Portulaca halimoides and P. suffrutescens is illustrated. Chromosome counts for the following species are provided: P. halimoides 2n = 18, P. smallii 2n = 18, P. amilis 2n = 18, P. rubricaulis 2n = 16, P. suffrutescens 2n = 8, and P. grandiflora 2n = 18. These data along with comments on morphology provide the documentation of characteristics needed to describe the species and write the key for the genus. A summary of trends in variability in the genus is given.