AbstractMosses exhibit a greater variety of cellular separation mechanisms than any other group of land plants. Diaspore liberation mechanisms range from (1) the random breakage of thin-walled stalk cells to (2) the formation of new internal walls that separate from the old walls, (3) severance along the middle lamella of the basal cell with or without the rounding off of the cells, (4) the formation of highly specialized abscission or tmema cells and (5) breakage along an intercalary region of thinwalled living cells. Rhizoidal gemmae are the only propagules lacking a separation mechanism other than by the decay of the filament system that produces them. In some species, two and sometimes three different kinds of diaspore are formed simultaneously in culture. Diaspore germination patterns in mosses are even more diverse than the liberation mechanisms. With a few exceptions new growth from diaspores is filamentous. Most diaspares are highly polarized and the germination pattern is fixed during development. Protonemal and rhizoidal gemmae are defined on the basis of the filament systems that produce them and from the presence or absence of specialized abscission mechanisms.