Life on Earth Kingdom Plantae Part II Rhyniophyta and Lycopodiophyta Cooksonia

Introduction Sporophyte generation (2N) is the photosynthetic, conspicuous generation All members have evolved specialized tissues for water (XYLEM) and food (PHLOEM) conduction Groups continue to become better adapted to the terrestrial environment

Evolutionary Lines PLANT KINGDOM “bryophytes” “vascular plants” “green algae”

Evolution of Non-Seed, Vascular Plants

Early Devonian Landscape (about 400 million years ago)

Reconstructed Early Devonian Landscape Cooksonia Aglaophyton Zosterophyllum early lycophytes Psilophyton

Phylum: Rhyniophyta Known from fossils more than 400 million years old (all extinct today) Sporophytes had no roots or leaves Sporangia produced only one kind of spore (homosporous) Example: Rhynia (found in chert beds in England)

Phylum: Lycophyta Plants with true roots and microphyllous leaves Some species produce compacted sporophylls into a cone or strobilus Some genera are homosporous (Lycopodium and Huperzia) others are heterosporous (Selaginella and Isoetes)

Heterospory vs. Homospory HOMOSPOROUS PLANTS gametophyte generation with archegonia AND antheridia (monoecious) spores male gametophyte with antheridia female gametophyte with archegonia HETEROSPOROUS PLANTS megaspores microspores dioecious gametophytes

Lycopodium Common in New England and the Great Lakes Region Often used for Christmas decorations (evergreen) Spores were once used as photographic flash powder

Lycopodium (strobili)

Selaginella Species are heterosporous with microsporangia and megasporangia Megaspores develop into female gametophytes Microspores develop into male gametophytes Large group with tropical, temperate and desert species

Selaginella rupestris

Selaginella with strobili

Selaginella striboli megasporangium microsporangium

Selaginella strobilus

Selaginella (sporangia) megasporangium microsporangium

Selaginella lepidophylla

Isoetes Commonly known as “quillworts” Each microphyllous leaf is a sporophyll, either a microsporophyll or a megasporophyll (heterosporous) Stem is a fleshy “corm” Often grow at the margins of ponds and lakes

Isoetes

Isoetes microsporangium

Isoetes

Isoetes melanopoda (Nebraska)

Lepidodendron Known as the fossil “scale tress” Common forest giant of the Carboniferous Period Helped to form present day coal deposits

Carboniferous Forest Reconstruction

Lepidodendron

Base of Lepidodendron (Stigmaria)