Fossil Whisk Fern Look Alikes

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

Rhynia Major Pteridophytes
Figure 21.1 Psilotum sporophytes. The small yellowish objects are three-lobed sporangia.

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.

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  • hamid teodros
    What plants have three lobed sporangia?
    5 years ago
    Why are wisk ferns important?
    5 years ago

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