1. How are ferns different from flowering plants or trees?
Flowering plants (including trees) produce seeds, while ferns produce spores. A chief difference between spores and seeds is that spores have very little stored food resources compared with seeds, and thus require more favorable conditions in order to successfully germinate. Seeds, therefore, are more resistant to harsh conditions and require less energy. Spores are usually produced in large numbers to increase the chances of survival.
2. Where is the true stem of a fern? What part grows above the ground? What is the most favorable environment in which ferns grow?
The true stem of a fern grows underground. All of the above-ground parts of a fern are known collectively as the frond. The part of the frond that looks like a stem is called the rachis (pronounced RAY-kiss).
Ferns have a popular image of growing in moist, shady woodland nooks, but the reality is far more complex. Ferns grow in a wide variety of habitats, ranging from remote mountain elevations to dry desert rock faces to bodies of water to open fields. Ferns in general may be thought of as largely being specialists in marginal habitats, often succeeding in places where various environmental delimiters limit the success of flowering plants. On the other hand, some ferns are among the world's most serious weed species, such as the bracken growing in the British highlands, or the mosquito fern (Azolla) growing in tropical lakes. There are four particular types of habitats that are often key places to find ferns: the afore-mentioned moist, shady forest cove; the sheltered rock face, especially when sheltered from the full sun; acid bogs and swamps; and tropical trees, where many species are epiphytes (an organism that grows upon or attached to a living plant).
3. How do ferns reproduce? Locate and describe three kinds of sori (from three kinds of ferns).
Fern Reproduction
Fern reproduction involves some big words, but we will break them down for you as they are introduced. There are two generations in a fern's lifecycle, the diploid generation, and the haploid generation. The diploid generation has a full complement of genetic material, while the haploid generation has only half the genetic material.
The life cycle of a typical fern is as follows:
- A mature fern, called a sporophyte fern produces spores through a process called 'meiosis (pronounced my-OH-sis). Each spore has only half the genetic material of the parent plant, a condition called haploid.
- The spores are dispersed
- A spore grows by cell division into a gametophyte - still with only half the genetic material of an adult organism.
- The gametophyte produces both sperm and eggs on the same organism using a process called mitosis (pronounced my-TOE-sis).
- The egg remains attached to the prothallus, but the sperm leaves the prothallus and swims to an egg on another plant which it then fertilizes.
- The fertilized egg is now has a full set of genetic material (and is called diploid) and grows into a sporophyte (the typical adult "fern" plant).
Kinds of Sori
4. How do spores travel from the parent plant to a new location? How long does it take a spore to develop into a mature plant? Observe from live ferns or pictures how a young fern is different from an adult fern.
Spores are stored by the fern in tiny cases called sporangia. These spore cases are massed together into a sorus (plural sori) which is visible to the naked eye on the underside of a fertile frond (not all fronds are fertile). The spore case is encircled by a ring consisting of a single layer of cells called an annulus. This ring goes almost all the way around the spore case. As the spore case dries out, it becomes brittle until it finally splits open. Since the ring is stronger than the rest of the spore case, it slowly pulls the case open. When water tension is released, the ring suddenly snaps, throwing spores out away from the fern at great speed. Because spores are so tiny (invisible to the naked eye), even the slightest breeze will carry them great distances.
If the spore lands in a location with favorable conditions, it will develop into a gametophyte in about two weeks. If the gametophyte is fertilized, it will grow into a young fern in about 3 and a half months. The amount of time required for these growth periods varies greatly depending on conditions and the species.
Below are examples of a young fern still in the fiddlehead stage, and a mature frond of the same species.
5. Know the medicinal uses of three ferns.
- Adiantum aleuticum (Western Maidenhair Fern)
- Frond tea is used to strengthen mucosal membranes, treat coughs, throat congestion, and respiratory irritation caused by air pollution.
- Asplenium scolopendrium (Hart's-tongue Fern)
- This fern had use in folk medicine as a spleen tonic.
- Cibotium menziesii (Hawaiian Tree Fern)
- The pith of the trunk is used in a combination of other Hawaiian plants to create a 'blood purifier', and is used in other combinations to help relieve weakness or chest pains. Heated fibres of the fronds are used to cure numerous bodily ailments such as muscle pain, stiff joints etc.
- Phlebodium aureum (Cabbage palm fern)
- Its uses include:
- for psoriasis and other skin conditions
- for Alzheimer's disease, dementia, and memory problems
- for coughs, bronchitis, chest colds, and other upper respiratory problems
- for autoimmune disorders
6. Draw or photograph ten kinds of ferns and properly identify them.
7. In addition to the common ferns there are fernlike plants known as club mosses and horsetails. Be able to recognize two club mosses and one horsetail. How are they similar to ferns?
Club moss is a term that describes the botanical family Lycopodiaceae (a family is one level up the hierarchy from the genus). Club mosses bear spores on specialized structures at the apex of a shoot; they resemble a tiny battle club, from which the common name derives. They are non-flowering and do not produce seeds.
- Lycopodium clavatum (Ground pine)
- This plant resembles a tiny pine tree. It grows in forests and sends runners underground form whence other plants spring.
- Lycopodium serratum (Toothed clubmoss)
- This plant is similar in appearance to L. clavatum. It prefers sandy to loamy soils in dappled or deep shade. The water-repellant spores can be used as a lubricant to keep things from sticking together.
- Lycopodium squarrosum (Tassle fern)
- These plants are also not true ferns. They are also similar to L. clavatum, but they "branches" hang from above somewhat like a weeping willow.
Horsetails, like club mosses and ferns bear spores rather than seeds. Horetails are in the order Equisetales which consists of a single family called Equisetaceae. There are 15 species in this order.
- Equisetum arvense (Field Horsetail)
- Equisetum arvense is a rather bushy perennial with a rhizomatous stem formation native to the northern hemisphere. These horsetails may have sterile or fertile stems. Sterile stems start to grow after the fertile stems have wilted. The sterile stems tend to be much taller and bushier, with the jointed segments being around one inch long with a diameter of about 1/20th of an inch. These segments contain one set of whorled, slender, erect branches each. Some stems can have as many as 20 segments and be as tall as 2-24 inches. The fertile stems tend to be half as tall as the sterile stems and also tend to be more succulent.
- Equisetum palustre
- E. palustre is a perennial horsetail, growing between 10 to 50 centimeters (4" to 20"), in rare cases up to 1 meter (3'). Its fertile shoots, which carry ears, are evergreen and shaped like the sterile shoots. The rough, furrowed stem is 1 to 3 mm in diameter with usually 8 to 10 ribs, in rare cases 4 to 12. It contains whorled branches. The tight-fitting sheaths end in 4 to 12 teeth. The lower sheaths are dark brown and much shorter than the sheaths of the main shoot. The central and vallecular are about the same size, but the carinal channels are much smaller. The central channels measure about one sixth of the diameter of the stem.
