Androdioecy in <i>Caltha palustris</i> (Ranunculaceae)

The article contains the first detailed report on androdioecy inCaltha palustrisL., a short-rhizomatous, fibrous-rooted herbaceous perennial, based on the studies conducted in the Moscow Region from 2021 to 2023.C. palustrisproduces flowers of two types: perfect and staminate (remains of carpels with non-functioning stigmas are preserved). Most of the studied individuals had larger perfect flowers, and their elements were always larger than those of staminate flowers. The studied populations consisted of three types of individuals: ones with perfect flowers only, ones with both perfect and staminate flowers, and ones bearing staminate flowers only. The synflorescence ofC. palustrisis a closed thyrsus, its subunits are dichasia. In andromonoecious plants, perfect flowers take a terminal position on both the thyrsus axis and in the dichasia of the paracladia, while staminate flowers are formed exclusively on the lateral axes of the dichasia. Most plants in the studied populations had perfect flowers (from 87.3 to 95.0%). Over a three-year observation period, the individuals of different sexual forms showed no evidence of sex change, and the ratio of different kinds of plants remained stable with only minor fluctuations.