In Marchantia, the gemmae are dispersed primarily by splashes of rain.
The gemmae are produced in a special cuplike structures, called gemma cups - located on the dorsal (upper) surface of the gametophyte.
One of the most familiar liveworts is Marchantia, a widespread genus that grows on moist soil and rocks. Its dichotomously branched gametophytes are larger than those of Riccia and Ricciocarpus.
Unlike the latter two genera, in which the sex organs are distributed along the dorsal surface of tyhe thallus, Marchantia has its gametangia borne on specialized structures called gametophores or gametangiophores.
The gametophytes of Marchantia are unisexual, and the male and female gametophytes can be readily distinguished by their distinctive gametophores.
Fragmentation is the principal means of asexual reproduction in liveworts, but another widespread mechanism is the production of gammae. When the gemmae disperse through splashing of raindrops, asexual reproduction occurs. The gemmae develop into new gametophytes. Primitive plants without vascular tissue requiring a moist habitat.
For more info and to see an illustration of the life cycle of Marchantia, see Biology of Plants by Peter H. Raven, Ray F. Evert, Susan E. Eichhorn.