| Abstract: | For better understanding of the relationships between genera, the primordium occurrence and morphological developmental process of female inflorescence, cymule and floret in Carpinus turczaninowii Hance and Ostryopsis davidiana Decne. of the Betulaceae were observed under the scanning electron microscope (SEM). Both species were monoecious. Their female inflorescence was a compound spike comprising several cymules arranged helically along an inflorescence axis. Each cymule consisted of two florets and five bracts, i.e., one primary bract and four other secondary ones which were developed from two semi-circular common primordia, respectively. In Carpinus , the adaxial secondary bracts grew slowly, while the abaxial ones grew fast, resulting in the appearance of a wide leafy bract upon maturity. In Ostryopsis , however, both abaxial and adaxial secondary bracts were fully developed, becoming a bladder-like but unclosed involucre when mature. Perianth primordia in both genera were circular. When the ovary became larger and larger, the perigone grew gradually, and finally surrounded and was adnate to the ovary. Some traditional viewpoints on the number of bracts and the orientation of bicarpellate ovary in cymule were clarified based on this study. The cymule bracts were not so many as those observed by Abbe; and the two bicarpellate ovaries were orientated perpendicularly, rather than parallel. |
