The Seedless Vascular Plants: Ferns and Their Relatives Chapter 18 Lecture Outline The Seedless Vascular Plants: Ferns and Their Relatives Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Outline Introduction Phylum Psilotophyta – The Whisk Ferns Phylum Lycophyta – The Ground Pines, Spike Mosses and Quillworts Phylum Equisetophyta – The Horsetails and Scouring Rushes Phylum Polypodiophyta – The Ferns Fossils

Introduction During early stages of vascular plant evolution: Internal conducting tissue developed. True leaves appeared. Roots that function in absorption and anchorage developed. Gametophytes became progressively smaller. Four phyla of seedless vascular plants: Psilotophyta, Lycophyta, Equisetophyta, Polypodiophyta

Introduction Psilotophyta Lycophyta Sporophytes have neither true leaves, nor roots. Stems and rhizomes fork evenly. Lycophyta Plants covered with microphylls. Microphylls - Leaves with single vein whose trace is not associated with a leaf gap Psilotum Lycopodium

Introduction Equisetophyta Polypodiophyta Sporophytes have ribbed stems containing silica. Have whorled, scalelike microphylls that lack chlorophyll Polypodiophyta Sporophytes have megaphylls that are often large and much divided. Megaphylls - Leaves with more than one vein and a leaf trace associated with leaf gap Equisetum A fern

Phylum Psilotophyta – The Whisk Ferns Resemble small, green whisk brooms Structure and form: Sporophytes: Dichotomously forking stems Above ground stems arise from rhizomes beneath surface of ground. Have neither leaves nor roots Enations along stems. Enations - Tiny, green, superficially leaflike, veinless, photosynthetic flaps of tissue Rhizoids, aided by mycorrhizal fungi, scattered along rhizomes.

Phylum Psilotophyta – The Whisk Ferns Reproduction: Sporangia fused in threes and produced at tips of short branches. Gametophytes develop from spores beneath ground. Branch dichotomously No chlorophyll Rhizoids aided by mycorrhizal fungi. Archegonia and antheridia scattered on surface. Zygote develops foot and rhizome. Rhizome separates from foot.

Phylum Psilotophyta – The Whisk Ferns Reproduction:

Phylum Psilotophyta – The Whisk Ferns Fossil whisk fern look-alikes: Silurian, 400 million years ago Cooksonia and Rhynia Naked stems and terminal sporangia Devonian, 400-350 million years ago Zosterophyllum Naked stems and rounded sporangia along stem Thought to be ancestral to club mosses

Phylum Lycophyta – The Ground Pines, Spike Mosses, and Quillworts Collectively called club mosses Two living major genera Lycopodium Selaginella Two living minor genera Several genera that became extinct about 270 million years ago Sporophytes have microphylls. Have true roots and stems

Phylum Lycophyta Lycopodium - Ground pines Often grow on forest floors Stems are simple or branched. Develop from branching rhizomes Leaves usually less than 1 cm long. Roots develop along rhizomes.

Phylum Lycophyta Lycopodium reproduction: Sporangia in axils of sporophylls. Sporophyll - Sporangium-bearing leaves In some species, sporophylls have no chlorophyll, are smaller than other leaves and clustered into strobili (singular: strobus). In sporangia, sporocytes undergo meiosis, producing spores.

Phylum Lycophyta Lycopodium reproduction: Spores grow into independent gametophytes. In some species, gametophytes resemble tiny carrots, develop in the ground and are associated with mycorrhizal fungi. In others, gametophytes develop on surface and are green. Archegonia and antheridia produced on gametophytes. Sperm are flagellated and water is essential for fertilization.

Phylum Lycophyta Lycopodium reproduction:

Phylum Lycophyta Selaginella - Spike mosses Especially abundant in tropics Branch more freely than ground pines Leaves have a ligule on upper surface.

Phylum Lycophyta Selaginella reproduction: Produce two different kinds of gametophytes = heterospory. Microsporophylls bear microsporangia containing microsporocytes, producing tiny microspores. Microspore becomes male gametophyte, consisting of an antheridium within microspore wall. Megasporophylls bear megasporangia containing megasporocytes, producing 4 large megaspores. Megaspore develops into female gametophyte consisting of many cells inside megaspore. Several archegonia produced where spore wall ruptures.

Phylum Lycophyta Selaginella reproduction:

Phylum Lycophyta Isoetes - Quillworts Most found in areas partially submerged in water for part of year. Microphylls are arranged in a tight spiral on a stubby stem. Ligules occur towards leaf bases. Corms have vascular cambium. Plants generally less than 10 cm tall.

Phylum Lycophyta Isoetes reproduction: Similar to spike mosses, except no strobili Sporangia at bases of leaves.

Surface of Lepidodendron, showing microphyll bases Phylum Lycophyta Ancient relatives of club mosses and quillworts: Dominant members of forests and swamps of Carboniferous, 325 million years ago Large, tree-like, up to 30 meters tall - Lepidodendron Surface of Lepidodendron, showing microphyll bases

Phylum Equisetophyta – The Horsetails and Scouring Rushes Equisetum Branched and unbranched forms, usually less than 1.3 meters tall Stems jointed and ribbed. If branched, then branches in whorls. Scalelike leaves in whorls at nodes. Stomata in grooves between ribs.

Phylum Equisetophyta Stem anatomy: Hollow central cavity from break down of pith Two cylinders of smaller canals outside pith. Carinal canals conduct water with xylem and phloem to outside. Vallecular canals outside carinal canals contain air. Silica deposits on walls of stem epidermal cells.

Phylum Equisetophyta Equisetum reproduction: Asexual by fragmentation of rhizomes Sexual reproduction: Strobili at tips of stems with sporangia connected to sporangiophores. Spores green with 4 ribbon- like elaters attached. Aid in spore dispersal Gametophytes lobed, green, cushionlike, up to 8 mm in diameter. Spores with elaters

Phylum Equisetophyta Equisetum reproduction:

Reconstruction of fossil giant horsetail, Calamites Phylum Equisetophyta Ancient relatives of horsetails: Flourished in Carboniferous, 300 million years ago. Human and ecological relevance: Many giant horsetails used for food by humans and other animals. Scouring rush stems used for scouring and sharpening. Reconstruction of fossil giant horsetail, Calamites

Phylum Polypodiophyta – The Ferns Structure and form: 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 - Referred to as fronds. Typically divided into smaller segments Require external water for reproduction

Phylum Polypodiophyta – The Ferns Reproduction: Sporophyte is conspicuous phase. Fronds, rhizomes, roots Fronds first appear coiled in crozier (fiddlehead), and then unroll and expand. Fronds often divided into segments called pinnae (singular: pinna). Crozier

Phylum Polypodiophyta – The Ferns Reproduction: Sporangia stalked. May be scattered on lower leaf surface, confined to margins, or found in discrete clusters called sori (singular: sorus). Sori may be protected by indusia (singular: indusium). With row of heavy-walled, brownish cells = annulus Annulus catapults spores out of sporangium. Sorus covered by indusium

Phylum Polypodiophyta – The Ferns Reproduction: Meiosis forms spores in sporangia. Spores released and grow into gametophytes called prothalli (singular: prothallus). Prothalli are one cell thick, and have archegonia and antheridia. Zygote develops into young sporophyte. Gametophyte, or portion of it, dies and leaves sporophyte growing independently.

Phylum Polypodiophyta – The Ferns Reproduction:

Phylum Polypodiophyta – The Ferns Fossil relatives of ferns: Devonian, 375 million years ago - Possible ancestors of ferns Resemble ferns in growth habit, but look more like whisk ferns Possible ancestors: Aglaophyton and Psilophyton

Phylum Polypodiophyta – The Ferns Fossil relatives of ferns Carboniferous, 320-250 million years ago - Tree ferns abundant Seeds found on some of fossil tree ferns.

Phylum Polypodiophyta Human and ecological relevance: House plants Function well as air filters Outdoor ornamentals Cooked rhizomes as food Folk medicine Fronds used in thatching for houses. Basketry and weaving

Fossils A fossil - Any recognizable prehistoric organic object preserved from past geological ages. Conditions of formation almost always include quick burial and an accumulation of sediments. Hard parts more likely preserved than soft parts.

Fossils Molds, casts, compressions, and imprints: After being buried in sediment and hardened into rock, organic material slowly washed away. If air space remains - Mold If silica fills space - Cast Compression - Objects buried by layers of sediment and overlying sheer weight compresses them to thin film of organic material and an outline. Image of an impression = imprint Coal is a specific type of compression. Compression fossil

Fossils Petrifactions - Uncompressed rock-like material in which original cell structure has been preserved Chemicals in solution infiltrate cells and cell walls, where they crystallize and harden, preserving original material. Coprolites - Dung of prehistoric animals and humans Unaltered fossils - Organisms fell into oil or water that lacked oxygen and did not permit decay. Petrified wood

Review Introduction Phylum Psilotophyta – The Whisk Ferns Phylum Lycophyta – The Ground Pines, Spike Mosses and Quillworts Phylum Equisetophyta – The Horsetails and Scouring Rushes Phylum Polypodiophyta – The Ferns Fossils