The sperm are released when the antheridium ruptures, thus allowing them to swim freely in a water film. After fertilization, many divisions form a multicellular embryo which is nourished by the gametophyte. Branch dichotomously . X-S of thallus shows many air chambers opening through a pore, lined with photosynthetic cells. Rhizoids function as roots.
Most liverworts grow where there is considerable moisture.
A. Riccia Widely distributed form, needing water for growth, but resisting drought successfully. Some forms aquatic, growing on water. Gametophyte Gametangia located in furrows on upper surface of thallus. Antheridium - sterile jacket surrounding many sperm. Sperm leave antheridium only when moisture is present for them to swim in.