Information here should be considered optional for the purposes of this class -- hornworts probably will not be available in the labs, and it's likely that you will not be expected to know the details of their structure or biology.

    Hornworts superficially resemble fern gametophytes or small thalloid liverworts. The thallus contains a few small air chambers, some of which may be inhabited by the symbiotic nitrogen-fixing cyanobacterium, Nostoc. Functional stomata first appear in the hornworts, although they are only present on the sporophyte. Unlike the sporophyte in liverworts, that of hornworts is strongly photosynthetic.