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The Seedless Vascular Pants: Ferns and Their Relatives Outline • • • • • Phylum Psilotophyta (Whisk Ferns) Phylum Lycophyta (Club Mosses) Phylum Equisetophyta (Horsetails) Phylum Polypodiophyta (Ferns) Fossils Phylum Psilotophyta • • The Whisk Ferns Loosely resemble small, green whisk brooms. Structure and Form - Sporophytes consist almost entirely of dichotomously forking aerial stems. Have neither leaves nor roots. Enations spirally arranged along stems. Life Cycle: Phylum Lycophyta • Ground Pines, Spike Mosses, and Quillworts Collectively called club mosses. - Only two living representatives of two major genera. Lycopodium Selaginella Sporophytes have microphylls. Have true roots and stems. Phylum Lycophyta • • Lycopodium - Ground Pines Often grow on forest floors. Resemble little Christmas trees, complete with cones. Stems are simple or branched. - Develop from branching rhizomes. Reproduction Phylum Lycophyta • • Selaginella - Spike Mosses Especially abundant in tropics. Branch more freely than ground pines. Leaves have a ligule on upper surface. Produce two different kinds of spores and gametophytes (heterospory). Reproduction Phylum Lycophyta • • Isoetes - Quillworts Most found in areas partially submerged in water, and least part of the year. Microphylls are arranged in a tight spiral on a stubby stem. Ligules occur towards leaf base. Corms have vascular cambium. Reproduction Phylum Equisetophyta • The Horsetails and Scouring Rushes Structure and Form - About 25 species scattered through all continents. - Significant silica deposits accumulate on the inner walls of the stem’s epidermal cells. - Branches, when present, are normally in whorls at regular intervals along the jointed stems. Phylum Equisetophyta • • • • Both branched and unbranched species have tiny microphylls in whorls at the nodes. Leaves fused at their base forming a collar. Stems are distinctly ribbed and have obvious nodes and internodes. Pith breaks down at maturity leaving a hollow central canal. Aerial stems develop from horizontal rhizomes. Reproduction Phylum Equisetophyta • Human and Ecological Relevance Many giant horsetails used for food. Scouring rush stems used for scouring and sharpening. Phylum Polypodiophyta • The Ferns Structure and Forms - Approximately 11,000 known species of ferns vary in size from tiny floating forms less than 1 cm to giant tropical tree ferns up to 25 m tall. Fern leaves are megaphylls that are commonly referred to as fronds. Typically divided into smaller segments. Spore Release From a Fern Sporangium Phylum Polypodiophyta • Human and Ecological Relevance Extremely popular house plants. - Serve as air filters. Cooked rhizomes serve as food. Folk Medicine Fronds used in thatching houses. Fossils • A fossil is generally defined as any recognizable prehistoric organic object preserved from past geological ages. Conditions of formation almost always include quick burial in an accumulation of sediments. - Hard parts more likely preserved than soft parts. Fossils • Molds, Casts, Compressions, and Imprints After being buried in sediment, the organic material may be slowly washed away by water percolating through the rock pores. - If air space remains - Mold - If silica fills space - Cast Compression takes place when objects are buried by layers of sediment and greatly compressed so that only a thin outline is left. Fossils • Petrifications Petrifications are uncompressed rock-like material in which the original cell structure has been preserved. Review • • • • • Phylum Psilotophyta (Whisk Ferns) Phylum Lycophyta (Club Mosses) Phylum Equisetophyta (Horsetails) Phylum Polypodiophyta (Ferns) Fossils Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display