About Ferns, Horsetails and Clubmosses
Ferns, Clubmosses and Horsetails are often grouped together as pteridophytes, a type of vascular plant (ie flowering plants, conifers, ferns, etc) that reproduces by spores rather than seeds. Even though they are often grouped together and have existed since before the time of the dinosaurs, the three groups (ferns, club mosses, and horsetails) are not at all related. The Horsetails consist of a single genus, Equisetum, with about 15 species worlwide. This genus is characterized by whorled, scale-like leaves. When branched the branches are also in whorls. Spores are produced in terminal cones, usually arising separately on a brownish cone on a single stem in the spring, followed by the sterile horsetail (the green part we are used to seeing) that remains all summer. Used since ancient times for scouring because stems are coated with silicon dioxide making them harsh to the touch. The clubmosses in our area all have small leaves with single veins; the leaves are generally spirally arranged on the stem, or may be opposite. Sporangium (spore producing sac-like structures) occur in cones or in the axils of modified leaves called sporophylls. In four genera there are about 1000 or so species worldwide, with more diversity found in the tropics.Ferns are much more varied than the other two groups with more than 10,000 species worldwide; about 100 species are found in northwest North America. Ferns have large leaves that are often divided into many leaflets (pinnae) and possess numerous veins. Ferns grow from a rhizome and stems generally grow horizontally at or near the ground surface. Spores are produced in sporangia that may be eusporangia which are relatively large and are found on special stalks in grape like structures. Or they may be leptosporangia which are formed in small clusters called sori that are found on the underside or at the margins of the leaves; these are smaller, produce fewer spores and are often covered by a protective membranous tissue called an indusium, they may also be covered by a rolled back leaf margin (false indusium). Life Cycle of Ferns, Horsetails and Clubmosses
When a spore lands in a suitable habitat it germinates into a small filamentous heart-, carrot- or top-shaped gametophyte. This gametophyte may be short-lived and photosynthetic, or it may be undergound with associated fungi and no chlorphyll and be long-lived. Eventually sperm are produced in spherical structures called antheridia and eggs are produced in flask shaped structures called archegonia. When mature the gametophyte of most ferns is a small heart shaped structure. From this grows a sporophyte (a young shoot) and the gametophyte then withers and dies. The sporophyte has roots, leaves and sporangia with well developed conducting tissues. This is the leafy green part of the plant that we see. Ferns Small: - Alpine Lady Fern (Athyrium alpestre), Oak Fern (Gymnocarpium dryopteris), Licorice Fern (Polypodium glycorrhiza), Maidenhair Fern (Adiantum pedatum), Maindenhair Spleenwort (Asplenium trichomanes), Parsley Fern (Cryptogramma crispa), Goldenback Fern (Pityrogramma triangularis), Narrow Leaved Sword Fern (Polystichum imbricans), Pacific Polypody (Polypodium amorphum aka P. montense), Leathery Grape Fern (Botrychium multifidum), Narrow Beech Fern (Thelypteris phegopteris).
Ferns Tall: Bracken Fern (Pteridium aquilinum), Lady Fern (Athyrium filix-femina), Sword Fern (Polystichum munitum), Deer Fern (Blechnum spicant), Spiny Wood Fern (Dryopteris expansa)
