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Menispermaceae is one of the core groups of Ranunculales. The single fertile ovule in each ovary in Menispermaceae varies greatly in integument number, micropyle formation, and integument lobe. However, data regarding ovule morphogenesis in the family are very limited. In this study, we document ovule development of selected species in the Menispermaceae using scanning electron microscopy and light microscopy. Ovule development in Menispermaceae shows the following characteristics. Two ovules are initiated in a young carpel, one of them degenerates gradually and the other develops into a fertile ovule in subsequent stages. Bitegmic in Sinomenium Diels. and Cocculus DC. and unitegmic in Stephania Lour. The formation of unitegmy is probably due to integumentary shifting. The annularly initiated inner integument is of dermal origin and has 2–3 cell layers in the family, but the semi‐annularly initiated outer integument is of both dermal and subdermal origin. Both inner and outer integument are cup‐shaped at maturity. The cup‐shaped outer integument is formed due to the outer integument's extension to the concave (adaxial) side of the funiculus. The obturator is well developed and consists of 2–3 cell layers in Cocculus or 9–11 cell layers in Stephania. Ovule development of Menispermaceae suggests some common characteristics between Cocculus and Sinomenium, and derived unitegmy supports molecular data that indicate Stephania is one of the late‐diverging lineages in the family. Integument lobations are present. The sterile ovule shows variations in the degeneration process. These results will provide evidence for exploring the evolution of ovules in Ranunculales. [ABSTRACT FROM AUTHOR]

Lardizabalaceae, one of seven families of Ranunculales, represent a monophyletic group. The family has functionally unisexual flowers with the organs in trimerous whorls, petaloid sepals and sometimes nectariferous petals. Among Ranunculales, Lardizabalaceae share several floral characters and climbing habit with Menispermaceae, but molecular analyses indicate that Circaeasteraceae and Lardizabalaceae form a strongly supported clade. Morphological and ontogenetic studies of flowers have proved to be a good complement to molecular data in clarifying relationships. Floral organogenesis has been studied in very few species of the family. This study investigates the comparative floral development of three species from three genera ( Decaisnea, Akebia and Holboellia) of Lardizabalaceae using scanning electron microscopy. Flowers have a whorled phyllotaxis. Within each whorl, the organs are initiated either simultaneously or in a rapid spiral sequence. In Akebia, six sepals are initiated, but one to three sepals of the second whorl do not further develop. The presence of three sepals in Akebia is thus a developmentally secondary simplification. The petals (if present) are retarded in early developmental stages; stamens and petals are different in shape from the beginning of development. The retarded petals may not be derived from staminodes in Lardizabalaceae. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, , 171-184. [ABSTRACT FROM AUTHOR]

• Stamen initiation and early development in male and female flowers are similar. • Staminodes in female flowers develop abnormally late with the anthers degenerating to different degrees. • Staminode morphology varies from staminiform, spoon-shaped, navicular, tongue-shaped to petaloid structures. • Anther wall formation is the basic type, simultaneous cytokinesis results in tetrahedral tetrads. The stamen is an extremely important reproductive organ in angiosperms. Androecia are the places where pollen is produced and show diversity in number and form; some are even reduced to staminodes or nectary structures in Ranunculales, but the development, morphology and structure of staminodes are completely unknown in Menispermaceae. In this study, the androecium development of Cocculus orbiculatus (L.) DC. was observed in detail for the first time under scanning electron microscopy and light microscopy. The results show that 1) stamen initiation and early development in male and female flowers are similar, while the staminodes in female flowers develop abnormally at later developmental stages, with the anthers degenerating to different degrees and becoming more or less flat structures; 2) in female flowers, the morphology and structures of staminodes are diverse: staminiform staminodes with tiny indehiscent anthers where 2-celled pollen grains or tetrads could be found in locules, or spoon-shaped, navicular, tongue-shaped and petaloid flat structures with an apex covered with secretions on the ventral surface; 3) in male flowers, the meiosis of the microspore mother cells occurs with simultaneous cytokinesis, the tetrads are tetrahedral, and the 2-celled pollen grains are tricolpate. In addition, the anther wall formation is the basic type. Compared to those of other groups in Ranunculales, the staminodes in Menispermaceae share some common characteristics with those of Lardizabalaceae, such as their position, number, size, morphology and degradation degree. [ABSTRACT FROM AUTHOR]