Just as our deciduous oaks are turning the hillsides golden brown in preparation for dropping their warm-weather foliage, early rains are bringing a carpet of green to the understory. This is the time of year for ferns, mosses, and liverworts to flourish. Found in damp, low-light areas, these are the oldest and structurally simplest land plants. Early relatives of ferns and mosses emerged 400 million years ago, long before dinosaurs.
Unlike the flowering plants we'll see later in the spring, ferns, mosses, and liverworts do not produce seeds. They reproduce with spores in structures called sporangia. While seeds have multiple cells that include the embryo, food for the embryo, and a coating for protection, a spore is a single cell.
In ferns, the spore-containing sporangia appear as dark dots that are easy to see on the underside of the fern blades. I've identified five different varieties of ferns on our property. My favorite is maidenhair fern. This deceptively delicate-looking plant has thin shoots, barely thicker than a hair, which some say is where it got its name. Ancient folklore suggests that a woman is still a virgin (maiden) if she can hold a stalk of maidenhair fern without the leaflets moving.
Liverworts and mosses are non-vascular, that is, they don't have water-carrying tissue like ferns and other vascular plants. Since diffusion moves water in and out of the plants, they depend on a wet environment. During World War I, sphagnum moss was used as a dressing on soldiers' wounds, a profound demonstration of its absorbency
The lifecycle of liverworts and mosses is divided into two stages. The gametophyte is the vegetative stage of leaves and stems from which the sporophyte or reproductive structure emerges.
Mosses grow in tufts or mats, often appearing as a velvet coating on rocks. This is the gametophyte stage. If you look closely, you'll notice tiny stalks emerging from the moss. These contain the reproductive spores..
The liverworts have the simplest structure of the three. The gametophyte, a flat-lobed leaflet called the thallus, looks a bit like a liver which is where its name originates. Wyrt is the Anglo-Saxon word for herb. In the Middle Ages, people believed plants resembled the organs of the body they could heal. Hence, doctors prescribed liverwort for liver ailments.
Our local liverwort, Astrella californica, might be overlooked because it is so small. Look for flattened green leaflets on shaded north-facing rocks and hillsides. By mid-February, the sporophytes will begin to sprout like tiny green umbrellas emerging from the thallus.
The ferns, mosses, and liverworts' need for moisture leads to a short "blooming" window. Come hot summer they will go dormant, waiting for the next winter's rain to rehydrate and reproduce.
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