The organization of the ranunculaceous flower with especial regard to the correlated variations of its constituent members

Abstract

Detailed analysis of numerous ranunculaceous flowers demonstrate that, though the meristic variation be wide, the numerical relations between stamens and ovule production are very similar for most species. The relatively unspecialized flowers of Helleborus are shown to exhibit a negative correlation between stamen numbers and ovule numbers, but more specialized folliculate genera (e. g. Aconitum, Delphinium ) were found to present a positive correlation. In Anemone , with one fertile and abortive ovules, there is positive correlation between stamen numbers and fertile ovules, as also in genera with a single fertile ovule in the carpel ( Ficaria, Hepatica, Ranunculus, Thalictrum ). Data showing the ratio between the average number of stamens and the average number of ovules (or uniovulate carpels) is provided for fifty species belonging to thirteen genera of Ranunculaceae. In general this ratio is shown to vary within narrow limits but Ranunculus sceleratus is an exception which though vegetatively stable exhibits a very low ratio and marked variability of the usually stable calyx. From a detailed study of over 1200 flowers of Ranunculus repens evidence is furnished that the degree of variation and the number of members in the respective floral whorls is under genetic control but that, in flowers from plants producing extra petals this control is relaxed and even the calyx exhibits appreciable variation while floral members sharing the characters of sepals and petals, or petals and stamens, are met with on these individuals. The exceptionally prolonged flowering season of this species in 1972 permits the recognition of a definite meristic drift but affecting normal and abnormal flowers differentially. It is concluded that though the flower of Ranunculaceae is very variable as to the numbers of its parts the numerical relations between the members of the different floral whorls, particularly in the more specialized species, or strains of species, are relatively stable.