The ultrastructure of the seeds surface of the subgenus Xyridion (Tausch) of genus Iris L. (Iridaceae) of the Flora of Ukraine

The surface ultrastructure of seeds coat of the subgenus Xyridion of the genus Iris L. from Ukrainian flora was examined. The studied seeds are characterized by both common and distinct features. The common features are: the shape and position of hilum (roundish, small, by position – basal); the shape and limits of cells of the test (polygonal, their boundaries are almost not visible); the character of thickening and tortuosity degree of anticlinal cell walls (uniformly thickened, straight). These features, as we suggest, could be additional diagnostic at the genera level. The distinct characteristics are: the type of cuticle; the type of seeds shape, the shape and the size of seeds. We suppose these characteristics as additional diagnostic at the species level. The seeds ultrastructure of I. pontica and I. sintenisii subsp. brandzae has been studied for the first time.