A hornwort is a bryophyte, or non-vascular plant, closely related to green algae. It is spore-producing and non-flowering. Although somewhat similar in appearance to liverwort, its name generally refers to the horn-like structure — called a sporophyte — which protrudes from the top of the plant’s greenish body. This wrinkly gametophyte body is flat and filmy, usually saucer-like, but may also be branched or rosette-shaped in appearance.
Most bryophytes, such as moss, are small, with hornworts being the smallest. These plant types usually anchor themselves via rhizoids, or root-like filaments. Generally, bryophytes have a gametophyte stage and a sporophyte stage. The gametophyte stage is normally the most dominant stage in the development process. The gametophyte dominates the plant’s life cycle, unlike other bryophyte plants.
In fact, the sporophyte of a hornwort plant remains attached and grows throughout its lifetime, making this its most dominant feature. The “horn” is photosynthetic, with only one chloroplast cell. The stomopyhte also has stomata-like openings, which exchange gases between the plant and the air. As it grows longer, the sporophyte eventually splits lengthwise, releasing spores. Once the spores germinate, new gametophytes are produced.
Although its origin still remains somewhat a mystery, the hornwort is though to be one of the oldest living land plants. It is believed to date back millions of years, as far back as the Cretaceous period. The plant remains rather inconspicuous to many people, having rarely been heard of. Nonetheless, there are roughly a hundred or so species of the plant found worldwide.
Normally found growing in damp, humid environments, hornwort plants may appear as small garden weeds, packed together like mats. They might also grow like an epiphyte on the bark of various trees, and are commonly found growing in shady, tropical-like forests or along streams and riverbanks. Occasionally, they may even be seen growing in moist, cultivated fields.
Under ideal conditions, such as tropical-like habitats, the plants act like a sponge, soaking up moisture in the air or from dew and rain and then slowly releasing it. Water is an essential factor for reproduction. Hornworts will not survive in dry conditions, as they simply break apart; yet, if it’s too wet, the plants are prone to rotting.