The Seedless Vascular Plants.docx

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Lakehead University
BIOL 1130
Dr.Marcus Freeman

The Seedless Vascular Plants: Ferns and Their Relatives Psilotophyta (Whisk Ferns) Lycophyta (club mosses) Equisetophyta (horsetails) Polypodiophyta (ferns) Four phyla -characterized by the presence of vascular tissue but still have spores not seeds and need water to reproduce. They have independent gametophyte and sporophyte and show alternation of generations. Age of Ferns Ferns were the dominant vegetation 350 million years ago. Shown below is a drawing of the prehistoric habitat. Most of the trees are giant club mosses. The frondlike leaves in the foreground are seed ferns. On the right is a giant horsetail. Phylum Psilotophyta The Whisk Ferns Loosely resemble small, green whisk brooms. Believed to be present since Silurian period ~ 400 million years ago Form Sporophytes consist almost entirely of dichotomously forking aerial stems. Have neither leaves nor roots. Enations –tiny green, leaf-like, veinless photosynthetic flap tissues -spirally arranged along stems. Life Cycle: Shows alternation of generations Phylum 1. Lycopodium-Ground Pines approx. 50 species Often grow on forest floors. Resemble little Christmas trees, Resemble little Christmas trees, complete with cones. Stems are simple or branched. Develop from branching rhizomes with roots. Leaves are small. Reproduction Diploid sporophyte –dominant. Spores are produced in spore bearing leaves called sporophylls. Sporophylls are arranged in a conical shaped structures at the terminal end of structures at the terminal end of a branch called strobilus. Sporangia are produced in the axils of sporophylls as kidney shaped structures. Sporocytes undergo meiosis to produce haploid spores –germinate into gametophyte. Phylum 2. Lycophyta - Selaginella-Spike Mosses –about 750 species. Especially abundant in tropics. Branch more freely than ground pines. Leaves have a ligule (tongue-like append.) on upper surface. Produce two different kinds of spores –microspores and megaspores (heterospory) germinating into two separate gametophytes Reproduction: Megasporophylls–produce megasporangium–in which 4 mega spores are produced Microsporophylls–produce microsporan
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