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The development of inflorescences and flowers of three species of Ranunculus and three allied genera ( Ceratocephala, Halerpestes, and Oxygraphis) (Ranunculeae, Ranunculaceae) was studied comparatively using scanning electron microscopy (SEM). Our results showed that both the inflorescence branching patterns and the floral morphogenesis in Ranunculeae are extremely labile. Inflorescences range from a thyrsoid to a solitary flower, with intermediate branching patterns in which sometimes only the terminal flower of the inflorescence main axis fully develops, such as in Ceratocephala and Halerpestes. Only in Oxygraphis is the flower truly solitary. In all species, sepal primordia are broad, crescent-shaped, and truncate, and the primordia of petals, stamens, and carpels are rather small and hemispherical, and very similar to each other. The plastochron between the last sepal and the first petal is relatively long. At the onset of androecium or gynoecium development, the regular spiral pattern of the perianth may become irregular in Ceratocephala and Oxygraphis, whereas spiral and whorled patterns may co-occur in Ranunculus and Halerpestes. The development of the petals is delayed with regard to that of the other floral organs in all species studied here, except for Oxygraphis. Our study confirms that, for solitary flowers, increased number of petals and the shape of the ventral nectary may have evolved independently many times, as suggested by earlier molecular phylogenetic studies and ancestral character reconstructions. With respect to the remainder of the tribe, Oxygraphis displays several autapomorphies, such as nondelayed development and increased number of petals, which will be of interest for comparative molecular developmental studies. [ABSTRACT FROM AUTHOR]

Abstract: Floral development and floral phyllotaxis in species of Adonis, Callianthemum, and Trollius (Ranunculaceae) were studied with scanning electron microscopy. The floral organs are initiated in spiral sequence and the flowers have spiral phyllotaxis. The sepal primordia are broad, crescent-shaped, and truncate, but those of petals, stamens, and carpels are rather hemispherical. A relatively long plastochron appears to be present between the last sepal and the first petal as compared with the short and equal plastochrones of all subsequent floral organs. Maturation of the stamens within the androecium appears to be centripetal. The carpels have a short ascidiate zone. Placentation is uniformly lateral, even in Adonis and Callianthemum, which have only one fertile ovule per carpel (versus median in other genera of Ranunculoideae with a single fertile ovule). In Adonis and Callianthemum at the tip of the carpel the ventral slit is gaping and the stigma is broadly exposed, whereas in Trollius the stigma is narrower and more pronouncedly decurrent along the ventral slit. The petals in Callianthemum and Trollius are more conspicuously delayed in development than those in Adonis as compared with sepals and stamens. A short carpel stipe is formed early in Callianthemum but later in Adonis and Trollius. In Trollius farreri (commonly having only five carpels in contrast to other species of Trollius) the carpels form a single (spiral) series. Thus floral development is similar in all three genera and, at a lower level, Adonis and Callianthemum are especially close but have different autapomorphies, which reflects the current classification of the genera. [Copyright &y& Elsevier]

• Floral structures are variable in Eranthis. • The stamen number is the main contributor to structural variation. • Morphological variation in Eranthis mainly occurred in petals. • Both sepal and petal numbers fit the modified error function. There is wide diversity in flower structure and pattern in nature. The number and morphological variation of flower organs in Eranthis of the family Ranunculaceae is high, but the pattern of flower structure variation in this genus is unclear. In this study, the morphological and numerical variation in organs of Eranthis stellata Maxim. and Eranthis lobulata W. T. Wang were observed with stereomicroscopy and scanning electron microscopy, and the patterns of variation were summarized statistically. The results showed the following: (1) The structural patterns of the two species of Eranthis were not stable. There were 232 flower structural patterns among 300 individuals of E. stellata and 55 among 100 individuals of E. lobulata. The number of floral organs in E. lobulata was significantly less than that in E. stellata. (2) The morphological variation in flower organs in Eranthis mainly occurred in petals, especially in the upper lip, pseudonectaries and lower lip, e.g., the number of lobes, and pseudonectaries and inconsistency in the upper lip edge. (3) The coefficient of variation (CV) of flower organs was greater than 20%, with some values close to 40%, which indicates that the number of floral organs of the two species differ substantially, and that the number of floral organs was extremely unstable. The range in stamen number was the largest while that in sepal number was the smallest, and this fluctuation might be caused by the spiral phyllotaxis of floral organs. [ABSTRACT FROM AUTHOR]