Wild About Illinois Ferns!

The ferns and their relatives (lycophytes) living today give us glimpse of what the earth’s vegetation looked like hundreds of millions of years ago when they were the dominant plants. Found in all but the coldest and driest environments, there are about 12,000 species of ferns and lycophytes worldwide, the third most numerous plant group after seed plants and bryophytes (mosses, liverworts, hornworts). There are 110 types of ferns in Illinois. Native ferns are important ecological components, and they can also be used for ornamentation, landscaping, fertilizer and food. These beautiful and curious plants provide excellent subjects for botanical education. The fascinating ferns are part of Illinois’ wonderful natural heritage!

Family: Dryopteridaceae
     bladder fern (Cystopteris bulbifera)
     Christmas fern (Polystichum acrostichoides)
     common woodsia (Woodsia obtusa)
     fragile fern (Cystopteris protrusa)
     lady fern (Athyrium filix-femina)
     marginal shield fern (Dryopteris marginalis)
     sensitive fern (Onoclea sensibilis)

Family: Aspleniaceae
     Bradley's spleenwort (Asplenium bradleyi)
     ebony spleenwort (Asplenium platyneuron)
     walking fern (Asplenium rhizophyllum)

Family: Thelypteridaceae
     broad beech fern (Phegopteris hexagonoptera)

Family: Ophioglossaceae
     common adder's-tongue (Ophioglossum vulgatum)
     rattlesnake fern (Botrychium virginianum)

Family: Polypodiaceae
     gray polypody (Pleopeltis polypodioides)

Family: Blechnaceae
     netted chain-fern (Woodwardia areolata)

Family: Pteridaceae
     northern maidenhair (Adiantum pedatum)

Family: Osmundaceae
     royal fern (Osmunda spectabilis)

People who study ferns (pteridologists) use some special terms to refer to the parts of a fern. The fern leaf is called a frond and is composed of the stipe and blade. When the frond is young, it unfurls from a coiled shape that resembles the curled end of a fiddle, thus the name fiddlehead is used. The fronds of many ferns arise from a horizontal stem that bears roots, a rhizome. If the fern frond is compound, the blade is divided into subdivisions called pinnae that attach to the rachis. In some species, the pinnae are further subdivided into pinnules. On the underside of the pinnule, small structures called sori are present. The sorus is sometimes covered by a protective tissue called the indusium. Inside are the sporangia that produce spores.

The life cycle of ferns and lycophytes involves two very different looking stages: the haploid gametophyte that makes gametes (sperm and egg) and the diploid sporophyte that makes spores. These plants do not produce seeds as are seen in flowering plants. The sporophyte is the phase familiar to most people. A typical life cycle, that of the marginal wood fern (Dryopteris marginalis), is illustrated. The frond (1) is composed of pinnae (2) which are divided into pinnules (3). This fern gets its name from the sori that are along the margins (edges) on the underside of the pinnules. The sorus (shown cut in half in 4) protects its sporangia by an umbrella-shaped indusium. One sporangium (5) contains 64 haploid spores that are produced by meiosis. The spores are dispersed from the sporangium by a catapult type mechanism. When they land on a moist surface, they germinate (6) and eventually form a prothallus (7) through a cell division type called mitosis. This gametophyte phase of the life cycle, seldom seen by people, is small, green and thin. On the underside of the prothallus two organs may form: the antheridium (8) and the archegonium (9). The antheridium produces many sperm that require water to swim to the archegonium that holds a single egg cell. When a sperm fertilizes an egg, a single-celled diploid zygote is produced. Although the prothallus shown here has both antheridia and archegonia, most ferns have mechanisms to prevent self fertilization. The zygote undergoes mitotic cell divisions to form an embryo and, with further development, a young sporophyte (10) that at first remains attached to the prothallus. With time the gametophyte disinte-grates, and the sporophyte grows into the large, leafy fern plant.

There are more than 100 species of ferns and lycophytes in Illinois, but half of them occur in nine or fewer counties and 30 of them grow in only one county. As with most plant conservation situations, a critical factor when protecting a species is preservation of its habitat. Natural habitats are continually being converted to other uses, resulting in the loss of native fern species. Other species may be at the edge of their natural range. The hay-scented fern (Dennstaedtia punctilobula) is rare in Illinois but more abundant in the eastern United States. Illinois represents the extreme western edge of this species’ distributional range. Many fern species grow only in specific areas and can thus serve as indicators of critical habitats. For example, cinnamon fern (Osmunda cinnamomea), sensitive fern (Onoclea sensibilis) and netted chain fern (Woodwardia areolata) all prefer wetland habitats. Others such as walking fern (Asplenium rhizophyllum) and purple cliff brake (Pellaea atrop-urpurea) prefer limestone substrates. The presence of broad beech fern (Phegopteris hexagonoptera) in an area may be a predictor of the presence of rare ferns and orchids.

Fern enthusiasts, collecting for home and garden, can negatively impact wild fern populations. In his book The Ferns of Florida (2000), Gil Nelson says “Given the number of responsible native nurseries that propagate and sell native fern species, coupled with the relatively low cost of such nursery-grown specimens, there is neither need nor justification for taking specimens from the wild.” A number of Illinois fern species can be easily cultivated. Growing ferns from spores provides an inexpensive means to assemble a diverse collection. For common species, such as maidenhair and Christmas fern, plants can readily be located outside of parks and natural areas. A single frond placed on paper for a day or so releases thousands to millions of spores that can be sown on moist, sterile potting soil. The gametophytes that result reproduce sexually thereby producing sporophytes that can be transplanted to pots or outdoor locations. The American Fern Society Web page and other sources give detailed instructions on how to grow ferns from spores. There are many advantages to landscaping with native plants, including drought tolerance, few predators, disease resistance and little required maintenance.

All of the fossil fuel (coal, oil, natural gas) used today derives from the fossil remains of large lycophytes and ferns that lived during the Carboniferous Period 300 million years ago.

The water fern (Salvinia molesta) can double its population size in just over two days. Three years after it was introduced to Kariba Lake in Africa, it covered over 390 square miles of water.

Bracken fern (Pteridium) and water clover (Marsillea) produce an enzyme called thiaminase that destroys thiamine, an important vitamin. Improper amounts of thiamine can cause nutritional problems and the disease called beriberi.

Some species in the genera Vittaria, Hymenophyllum and Trichomanes are known in North America only as gametophytes. The sporophyte generation (with fronds) never forms.

Some tropical fern and Selaginella species live in deep shade and glow an iridescent blue-green.

A single plant of the marginal wood fern (Dryopteris marginalis) can produce 67 million spores.

About half of the fern species on earth today are polyploid, that is, they have extra sets of chromosomes (often following hybridization). Despite this, many of these “extra” genes are silenced, and the species behave genetically like diploids.

antheridium - the male organ on the prothallus that produces sperm cells

archegonium - the female organ on the prothallus that produces the egg cell

blade - the broad, upper part of the leaf, as opposed to the stipe

chromosome - structure within the cell nucleus that contains DNA

diploid - with two sets of chromosomes

egg - the female sex cell

embryo - the young sporophyte that forms from the zygote

fiddlehead - the young leaf that is still coiled

frond - the fern leaf, composed of a stipe and a blade

gametophyte - the haploid plant that produces sex cells (gametes)

haploid - having one set of chromosomes

indusium - a tissue that covers and protects the sorus

meiosis - a cell division type that halves the chromosome number in the four resulting cells

mitosis - a cell division type where the chromosome number of the two resulting cells remains the same as the original cell

pinna - (pl. pinnae) – a subdivision of the leaf blade that is fully separated from the rachis

pinnatifid - a frond or pinna that is cleft or lobed only part way to its axis

pinnule - a subdivision of the pinna

prothallus - the flat, often heart-shaped gametophyte

rachis - the upper stalk of the blade where the pinnae attach

rhizome - a horizontal stem, often just below ground

sorus - (pl. sori) – a grouping of sporangia on the underside of the pinnae or pinnules

sperm - the male sex cell

sporangium - the small capsule that bears the spores

spore - small, single-celled body produced via meiosis that forms within sporangia

sporophyte - the diploid plant that produces spores

stipe - the lower stalk of the blade

zygote - the cell that is the immediate product of fertilization (egg plus sperm)

Cobb, B., E. Farnsworth, and C. Lowe. 2005. A field guide to ferns and their related families of northeastern and central North America. 2nd edition. Houghton Mifflin Co. New York. 415 pp.

Flora of North America Editorial Committee. 1993. Volume 2, pteridophytes and gymnosperms. Oxford University Press, New York. 475 pp.

Hoshizaki, B. J. and R. C. Moran. 2001. Fern growers manual. Timber Press, Portland, Oregon. 604 pp.

Moran, R. C. 2004. A natural history of ferns. Timber Press, Portland, Oregon. 301 pp.

Mohlenbrock, R. H. 1999. The illustrated flora of Illinois – ferns, 2nd edition. Southern Illinois University Press, Carbondale, Illinois. 240 pp.

Mohlenbrock, R. H. 1986. Guide to the vascular flora of Illinois. Southern Illinois University Press, Carbondale, Illinois. 507 pp.

Smith, A. R., K. M. Pryer, E. Schuettpelz, P. Korall, H. Schneider, and P. G. Wolf. 2006. A classification for extant ferns. Taxon 55: 705–731.

The Illinois Department of Natural Resources provides additional information and resources about ferns and lycophytes in our state. The Division of Natural Heritage monitors populations of plant species and makes and implements management options. The Division of Ecosystems and Environment reviews development plans proposed by state and local governments and recommends measures to reduce or avoid adverse impacts to threatened or endangered species and their habitats. The Education Section provides educational materials and teacher training on a variety of natural resources topics and offers grants for schoolyard wildlife habitat development and field trips for students. Many publications related to plants and wildlife habitat development are available through the publications order form.