SporePlants213 - Spore-Dispersing Vascular Plants - 1 The...

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Unformatted text preview: Spore-Dispersing Vascular Plants - 1 The vascular plants are divided artificially into two major groups, the seedless (or spore-dispersing) vascular plants and the seed plants. There are four major Phyla of spore-dispersing vascular plants plus three extinct phyla for which excellent fossils remain. The spore-dispersing vascular plants include the: Rhyniophyta Extinct Zosterophyllophyta - Extinct Trimerophytophyta - Extinct Lycophyta (Lycopodiophyta) Lycopodiae Selaginellae Isoetae Monilophyta or Pteridophyta* (sometimes Pterophyta) Equisetales (Sphenophyta) Psilotales (Psilophyta) Ferns (Pterophyta) Ophioglossales Eusporangiate Marattiales Eusporangiate Filicales Homosporous and Leptosporangiate Salviniales Heterosporous and Leptosporangiate Marsileales Heterosporous and Leptosporangiate * Traditionally, the groups now clustered into one phylum were considered to be separate phyla, with the name Pterophyta used just for the Ferns. For ease of discussion in Biology 213, the five orders within the ferns will be considered as one group, using the former phylum name, Pterophyta. The earliest vascular plants have been reconstructed from the fossil record dating back about 425 million years, with branching sporophytes that were nutritionally independent of the gametophyte. The early vascular plants were small, as are the Bryophytes but their branching patterns provided a means of increasing complexity of the plant body and support for multiple sporangia. However, early vascular plants lacked roots or leaves. The ancestors of the Lycophyta, Equisetales and Psilotales, extant vascular plants often referred to as the "fern allies", were the first large land plants. Lycophytes and Equisetums are also prevalent in the fossil record. These vascular plant groups are not predominant organisms in our ecosystems today, substantially being replaced in ecosystems by seed plants. In contrast, the ferns, within the phylum, Pterophyta, are conspicuous in many ecosystems, including the Pacific Northwest. Spore-Dispersing Vascular Plants - 2 Early Vascular Plant Reconstructions Fossil Lycophyte Tree Carboniferous Forest Reconstruction Spore-Dispersing Vascular Plants - 3 Lycophyta (Lycopodiophyta) Members of the Lycophyta were once abundant on earth. There are extensive fossil records of these vascular plants, and their decomposing bodies produced much of today's fossil fuels. Fossil Lycophytes ranged up to 100 feet tall. Today there are ten to fifteen genera in the Lycophyta; none are dimensionally impressive. There are about 700 species of Selaginella , 400 species of the Lycopodiae genera, and fewer of the elusive Isoetes . Representatives of all three classes of the Lycophytes are found in Washington and the Pacific Northwest. Each class has unique morphological features so that it is not easy to discuss the Phylum....
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SporePlants213 - Spore-Dispersing Vascular Plants - 1 The...

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