Athyrium thelypteroides
Description:
The Athyrium thelypteroid is a fern species which botanists have grouped together as pteridophytes, defined as those tracheophytes or vascular plants that are spore producing rather than seed producing. There is great antiquity with the fern group dating back 350 million years. With over 400 generas and over 12,000 species they reside in an extraordinary range of habitats from high altitude Arctic Alpine to the mid tropical rainforests and sub-desert continental interiors all the way to the rock sea coasts and swamps.
| Athyrium thelypteroid, (Silvery Spleenwort, Silvery glade fern) | |
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| Species: | A. thelypteroides (Michx.) Desv.
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| Athyrium thelypteroides | |
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Deparia acrostichoides | |
The large leaf blade, or fronds, of the Athyrium thelypteroid on average could be from 40 inches in length and 11 inches in width to as long as four feet in length. Their texture is somewhat thin and they tend to be erect and clustered on the plant. Each finely cut frond contains many pinnae, (leaflets). Each pinnae have multiple pinnule on which a central vein is visible and on the fertile fronds the sori and the indusium are present on the underside. They produce a limited number of spores, generally 32 or 64.
Fern reproduction
Fern spores in suitable habitat germinate and develop into small filamentous gametophyte called prothallus. The short-lived photosynthetic gametophyte can be above ground or below ground as a symbiotic long-lived associate with fungi. The sex organs which contain the gametes are eventually produced. The egg is produced in the archegonia and the sperm are produced in the antheridia. Resulting from fertilization the zygote is divided into several celled embryo with regions as foot, root, shoot, and leaf.
The predominate mode of breeding in most fern species is by cross fertilization. The developing embryo produces a young shoot, the sporophyte. After the first leaves, the root and shoot are produced and the original gametophyte whithers and dies. Thus the sporophyte becomes independant of the gametophyte.
Polyploidy is an outstanding feature of ferns and is estimated to occur in roughly 50-60% of all cytotypes. Polyploidy is frequently associated with increased amount of spore and stomatal length. Within a species, not at random, an increase in ploidy was associated with an increase spore size.
The chromosome number of A. thelypteroides is 2n=80.
The stem usually grows horizontally or slightly below ground and is called the rhizome. The rhizomes of the A. thelypteroides are short-creeping and therefore form close colonies of the plants. They form vegetative fronds in spring time and continue to grow other fertile fronds during mid-summer. The fertile fronds are somewhat narrower and more erect than the vegetative fronds. The vegetative blade's cross section shows two stipe bundles.
The silvery appearance of the young indusia is credited for the common name of 'silvery spleenwort'. The sori are distinctive with their elongated shape.
Habitat:
The A. thelypteroides can be found in areas with moist soil. More typically in woody slopes or along stream banks in alluvial soil. Athyrium tend to thrive between boulders, humid crevices in between rocks, where they are the dominant vascular plants.
Distribution Range:
A. thelypteroides can be found on North America and in Asia. In the U.S. the A. thelypteroides can be found from southern GA, eastern MO, MI, and up to MN.
References
- Wiley, Farida A. (1936). Fernsof NorthEastern U.S.. New York, US: Dover Publications.
- Montgomery, James D.; Fairbrothers, David E. (1992). New Jersey Ferns and Fern-Allies. New Jersey, US: Rutger University Press.
- Dyer, A.F. (1979). The Experimental Biology of Ferns. London, Great Britain: Academic Press Inc.
- Vitt, Dale H.; Marsh, Janet E.; Bovey, Robin B. (1988). Mosses Lichens & Ferns of Northwest North America. Alberta, Canada: Lone Pine Publishing.
- Wherry, Edgar T. (1961). The Fern Guide. New York, US: Doubleday & Company, Inc.
- Bower, F.O. (1963). The Ferns. New Delhi, India: Today & Tomorrow's Book Agency.
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