Monoicy (/mɒˈnoʊəsi/) is a sexual system in haploid plants (mainly bryophytes) where both sperm and eggs are produced on the same gametophyte, in contrast with dioicy, where each gametophyte produces only sperm or eggs but never both.[1][2] Both monoicous (/mɒˈnoʊəkəs/)[3] and dioicous gametophytes produce gametes in gametangia by mitosis rather than meiosis, so that sperm and eggs are genetically identical with their parent gametophyte.
It has been suggested that monoicy may have benefits in dry habitats where the ability to produce sporophytes is limited due to lack of water.[4]: 292
Monoicy is similar to, and often conflated with, monoecy, which applies to seed plants (spermatophytes) and refers to separate male and female cones or flowers on the same plant.
^Crandall-Stotler, B.J. & Bartholomew-Began, S.E. (2007). Morphology of Mosses (Phylum Bryophyta). In: Flora of North America Editorial Committee, eds. (1993+). Flora of North America North of Mexico. 16+ vols. New York and Oxford. Volume 27, 2007.
^Bell, P.R. & Helmsley, A.R. (2000). Green plants, their origin and diversity (2nd ed.). Cambridge University Press.