ИСТИНА

Despite extensive debates on taxonomy of Ruppia, most accounts recognize at least two species, R. maritima and R. cirrhosa. We compared inflorescence morphology and vascular anatomy in these two species. Apart from inflorescences of typical structure (open spikes with two flowers) both R. maritima and R. cirrhosa develop spikes with at least partially fused flowers. R. maritima has a tendency to reduction in the number of flowers to one, while R. cirrhosa tends to increase the number of flowers up to three. In both species, complete fusion of two lateral uppermost flowers results into a terminal flower-like structure of unstable morphology. The species differ in presence or absence of stamens with inverted polarity in abnormal inflorescences. Our results contribute to understanding possible pathways of evolutionary transformations in flowers and inflorescences.