(hornworts, horned liverworts) A class of the *Bryophyta
containing a single order, Anthocerotales, and some five genera. Members of this order are distinguished from those of liverwort orders, with which they are sometimes classified, by their long-lived axial sporophytes. These contain photo-synthetic tissue and stomata and occasionally persist after the death of the thallose gametophyte. Most species are also unusual in having a single pyrenoid-containing chloroplast in each cell, a feature reminiscent of the algae.