In order to increase our embryological knowledge of Pereskia, a genus considered the earliest member of Cactaceae, we followed the development of the flowers and seeds of Pereskia lychnidiflora, a species from southeastern Mexico. We compared our data with that available from other closely related members in the family. The embryological characterization showed that basic features are homogeneous across the family and supported the placement of P. lychnidiflora as a member of one of two Pereskia clades, the one sister to remaining cacti. Our data also supports the hypothesis that within the family Cactaceae, the evolutionary tendency is towards a reduction of the perisperm. A multilayered seed coat was observed in P. lychnidiflora. A novel finding was the presence of stomata along the basal and central part of the ovary, a character that has never been reported before in other members of Pereskia.