A Time for Bryophytes

Winter is a time for the Bryophytes which includes the mosses, liverworts, and hornworts. Recently when I was out evaluating the inundation on the northern end of the valley, I discovered an area where all three of these plant types are growing. This blog is mostly about hornworts, since it is the first time I have seen them on the mitigation lands.

A little overview of Bryophytes before I talk about hornworts:

Bryophytes are thought to be the oldest land plants and the link between land and aquatic plants. The oldest records (which are very few since they don’t contain any lignin) date back to almost 500 million years ago.

Bryophytes play a key role in soil formation and maintaining soil moisture, in addition to nutrient cycling.

Bryophytes do not have flowers, roots, or stems.

Like amphibians, all bryophytes need water to successfully reproduce. They have been called the ‘amphibians’ of the plant world. Bryophytes are non-vascular plants, or more correctly, non-tracheophyte plants, which means they do not contain the system of channels that other plants have to conduct water, food, and minerals through-out the plant. They all reproduce with spores and have two distinctive stages, the sporophyte and the gametophyte. The sporophyte produces spores that develop into new plants and the gametophyte is the adult plant that has the male or female reproductive structure, or both.

These plants have other ways to reproduce asexually such as a small piece breaking off and growing into an adult, or with structures called gemmae that are specialized groups of cells that can grow into an adult plant.

The sporophyte part of a moss, liverwort, and hornwort is often the most noticed feature of the plant because they grow up from the plant and have interesting forms. A moss sporophyte is a thin filamentous thread-like stalk with a capsule at the end that comes in many shapes from cylindric to round to ovoid. These usually come out of the gametophyte, the leafy green plant. Even though generally quite small, they can be 3.5 inches or more tall. Their colors vary from yellow to red to purple. The sporophytes of some liverworts are like a fringed umbrella and are shorter than most of the moss sporophytes.

Now we get to the hornworts! You may never have seen these diminutive plants. They can look like algae on the banks of a creek with their light green, slimy and translucent leaves, called thalluses or thalli. Interestingly they are indeed closely related to some species of blue green algae. The name, hornwort, is fitting because their sporophytes resemble slender horns and wort means small.

The “horns” split open to let the spores out when the spores are mature. Unlike liverworts and mosses of which there are thousands of species, it is believed that there are only 100 to 300 species of hornworts in the world and only six genera! This is a relief to me since it is not as nearly overwhelming as learning all the moss and liverwort species! The area where I found the hornworts is a muddy, wet area all winter long. Water runs through small channels across a meadow and into a woodland. I have also found hornworts off mitigation lands in seeps, along roadcuts, and trail cuts. The more I look the more of them I find. Take some time to look around where you live and there will probably be some hornworts growing.