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Ferns (Division Tracheophyta)
Ferns are vascular plants. These are plants, like wildflowers and trees, that have a system of internal vessels for transporting fluids, but unlike flowers and trees, ferns have no flowers and seeds. Instead they reproduce mostly by spores. There are about 15 species of ferns common in the Pacific Northwest, some of which we see between the capes. Most of us are familiar with the habit of ferns - the pinnate leaves or fronds with their feather-shaped blades and stipes branching from rhizomes that are often underground. Roots anchor the plant to the ground or, in some cases to trees. Like algae and other lower plants, ferns have gametophyte and sporophyte generations. The gametophyte, which produces eggs and sperm, is usually small and inconspicuous. The fertilized egg from the gametophyte gives rise to the much larger and more familiar fern that we see in the woods, the sporophyte plant that produces spores. In most ferns there are two kinds of fronds, sterile and fertile (spore producing), both on the same plant, a condition called dimorphism when the two fronds have distinctive forms.
The spores are produced and carried in small containers called sporangia, usually on the lower side of the frond (see article on the Sword Fern). These sporangia are generally in clusters called a sori (sorus - singular), sometimes arranged in rows or at the margins of a pinna. The sorus is often covered by a thin membrane, the indusium, which may confer some protection to the sporangia. The shapes and arrangements of the sori and their indusia are important in species identification. Text and Photos by Jim Young Click on image for more information.
