Studies on the development of common lilac cv. Mme Florent Stepman inflorescence buds and flowers were carried out in 2001-2002 in order to observe the development of flower organs before and after winter dormancy during the following phenological phases: inflorescence bud swelling, inflorescence elongation, flower bud whitening, flower bud swelling and flowering anthesis. The hypogynous, actinomorphic and perfect flower conforms to the general pattern of the Oleaceae. The calyx is four-lobed, and the four-lobed corolla is gamopetalous with a cylindrical basal tube. Two stamens are basally fused with the corolla. The anthers are tetrasporangiate, with a uniseriate epidermis, bilayered endothecium, single middle layer, and secretory, binucleate tapetum. Microspore tetrads are isobilateral and the pollen grains are spherical, three-colpate and two-celled. The ovary is superior and bilocular. Four anatropous, unitegmic and tenuinucellar ovules are formed. The female gametophyte development is Polygonum-type. Flower primordia differentiation starts in midsummer and lasts until autumn. Before entering dormancy, microspore meiosis was discernible in flowers in the lower part of the inflorescence. The ovular primordia differentiate after winter dormancy. During inflorescence bud breaking after winter dormancy, pollen mother cells in anthers and ovule primordia were observed. During inflorescence elongation, pollen mother cell meiosis and microspore tetrads occured in anthers, and the archesporial cell of the megaspores was present in ovules. During flower bud whitening and flower bud breaking, young microspores were observed in anthers, and developing megaspores were visible in ovules. In the last phenological phase, anthers dehisced and the female gametophyte was organized.
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