Fossil plants that somewhat resemble whisk ferns have been found in Silurian geological formations (Table 21.1). These formations are estimated to be as much as 400 million years old. One group of these fossil plants, of which Cooksonia and Rhynia are examples (see Fig. 21.22), had naked stems
and terminal sporangia. Cooksonia is the oldest plant known to have had xylem. A second group of fossils, represented by Zosterophyllum, had somewhat rounded sporangia produced along the upper parts of naked stems. Zosterophyllum and its relatives first appeared during the Devonian period (Table 21.1). They are thought to be ancestral to the club mosses, discussed in the next section, "Phylum Lycophyta—The Ground Pines, Spike Mosses, and Quillworts."
Whisk ferns are of little economic importance. Their spores have a slightly oily feel and were once used by Hawaiian men to reduce loincloth irritations of the skin. Hawaiians also made a laxative liquid by boiling whisk ferns in water.
Was this article helpful?
Are You Striving To Look And Feel Youthful? Wish You Could Add 20 Years To Your Life? Discover the Secrets to a Longer, Healthier Life With This Fantastic Anti-Aging Resource. You might be feeling and looking great now, but have you ever thought about what youll feel and look like several years from now? Have you ever considered that the choices you make today directly influence how well you age?