The group of plants popularly known as liverworts comprise the first two of the following three classes of the division Bryophyta (bryophytes):
Class I HEPATICOPSIDA (Hepaticae).
Class II ANTHOCEROTOPSIDA (Anthocerotae).
Class III BRYOPSIDA (Musci or mosses).
In New Zealand there are, on the whole, fewer liverworts than mosses, though in very wet places, such as Fiordland and the southern part of Stewart Island, liverworts may predominate, both in terrestrial and in arboreal situations. They grow luxuriantly in wet areas and, with the mosses, form a feature of the rain forest. Mosses and liverworts are botanically distinct, the liverworts having a greater variety in their vegetative organs and in the disposition of the sporophytes. As in the mosses, the life cycle of the liverworts involves a well marked alternation of generations. The gametophyte or sexual generation bears the organs of reproduction which produce the sporophyte or the asexual generation. This grows out of the gametophyte, or “plant” as we know it, and draws sustenance from it. The sporophyte in its turn develops spores which may “germinate” into a small intermediate short-lived structure called the protonema, which gives rise to the gametophyte or “plant”, and thus completes the cycle.