Floral morphogenesis of Anemone rivularis Buch.-Ham. ex DC. var. flore-minore maxim.: (Ranunculaceae) with special emphasis on androecium developmental sequence

The floral morphogenesis and androecium developmental sequence of Anemone rivularis Buch.-Ham. ex DC. var. flore-minore Maxim. were observed under a scanning electron microscope (SEM) and by means of histological methods in order to expand our knowledge of the morphogenesis and development of the floral organs of the Ranunculaceae. The initiation of the floral elements is a centripetal spiral and the direction of the spiral is clockwise or anti-clockwise. However, the development of the androecium is highly unusual: in a longitudinal series of four stamens, the second stamen develops first from the inner to outer, then the third one, the fourth one and the first one in turn. The microsporogenesis and anther maturation follows the same developmental sequence. The tepals are different from the bracts and the stamens in both shape and size in the early developmental stage, but there is no difference between the stamens and carpels in the early developmental stage. Therefore, we established a spatio-temporal process of the floral morphogenesis of A. rivularis var. flore-minore and offer another meaning of the floral diversity patterns attributed to the level of the genus.