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| There are a few key characteristics which distinguish ferns from other plants. The most obvious is the absence of flowers, fruits and seeds. Ferns reproduce by spores. Spores are typically produced on the underside of the fern leaf in clusters called sori. The original classification of the ferns were based on the position and shape of these spore-producing organs. The life-cycle of ferns alternates between two very distinct generations. The fern plant, as most people are familiar with, is the sporophyte generation and it produces dust-like spores. Spores will germinate into minute gametophytes measuring less than 1 centimeter. It is the gametophyte stage which produces male sperm and female eggs and once united, the sporophyte develops. |
 Polypodium fern with sori |
 An emerging frond or fiddlehead Photo by: Andrew G. Seymour |
Although mature ferns consist of roots, stems and leaves, just as other plants do, different terms are often used to describe the various fern parts. Fern leaves are called fronds and the stem is called a stipe.One fairly distinctive feature among ferns is the manner in which the newly emerging foliage unfolds in a scroll-like fashion. The newly developed fern leaves are called fiddleheads. Rhizomes are another distinguishing characteristic common among many ferns. These stuctures not only provide a vital link between the roots and the frond, but also determines the plant's habit. Rhizomes and fronds are often clothed with a protective covering of hairs and/or scales. Rhizomes may be erect, holding the frond in a close, vase-like cluster, or it may creep horizontally, with fronds arising in an irregularly. |
 Salvinia auriculata - Water Spangles |
 Azolla sp. - Mosquito Fern |
| There are a number of ferns that live on or in water. These aquatic ferns display hundreds of fine translucent hairs that hang down in the water below them, absorbing nutrients for the plant just as true roots. Floating ferns in their natural setting provide cover for fish and other animals, and some are food to certain types of fish. | |
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The fern allies are relatives of the ferns. Like the ferns, they have the alternation of generations and they reproduce from spores. The fern allies differ mainly from ferns in that they do not have the same leaf structure. Whisk ferns are essentially leafless, the leaves of horsetails are reduced to scales and the club mosses display minute single-veined leaves. The horsetails, called such because of their resemblance to horses' tails, are also called scouring rushes. The plants, which have silica deposits along the stems, were often used for scrubbing pots and pans. The jointed stems can be branched or unbranched, with some species reaching 15 feet. The leaves are non-photosynthetic and are nothing more than small scales surrounding the nodes. Club mosses and Spike mosses are, perhaps, the fern allies which most resemble ferns. The club mosses and spike mosses have true stems and roots, and the tiny leaves, called microphylls, have a single vein. Selaginella, a spike moss, branches freely, often with the branches rooting as they creep along the soil surface. Selaginella albomarginata is pictured at the top left of this page. |
 Equisetum sp.  Psilotum nudum Photos by: Andrew G. Seymour |
| The Whisk Ferns, leafless shrubs about 12 inches tall, are called such because of their resemblance to a small whisk broom. The conspicuous green plant, the sporophyte, consists of branching stems which arise from underground rhizomes. Photsynthesis occurs in the aboveground branching stems. No roots are present, the rhizome performs the functions of a root. In Psilotum, the leaves are small, scalelike outgrowths without vascular tissue. Occasionally, small, round yellow pouches of spores, called sporangia, appear along the branches. | |