Аннотация:Species of Tofieldia show differences in floral vasculature that can be correlated with differences in floral morphology, including number of vascular bundles in the pedicel, origin of carpellary bundles, and variation in the vasculature of the ascidiate zone. The presence of a calyculus is a unique synapomorphy of Tofleldiaceae. Structural differences in calyculus between various species of Tofieldia influence differences in calyculus vascularization. In most species, the calyculus is separated from the flower by a shortened internode; it receives its vasculature from the pedicel. In species that possess three equal-sized calyculus scales, these are all vascularized, but in species with a small median calyculus scale, the smallest scale consistently lacks vasculature. In T. pusilla, which apparently lacks a flower-subtending bract, the calyculus is shifted to the base of the pedicel and receives its single bundle from the peduncle. Both morphologically and developmentally, the median calyculus scale of T. pusilla resembles a flower-subtending bract, indicating a 'hybrid' nature for this organ, which is supported by our anatomical studies.
Keywords: Alismatales, anatomy, calyculus, flower.