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Chapter 21 Vascular Plants Without Seeds, Cross-link Description:…

- - - - have dibiontic life cycle
        
        each species has
        
        multicellular gametophyte
        
        multicellular sporophtye
        
        how did sporophytes come into existence
        
        interpolation hypothesis
        
        small sporophyte generated when
        
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        alternative hypothesis
        
        transformation theory
        
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  - - - zygote undergoes only meiosis
        
        producing spores that
        
        grow into new gametophytes
        
        cannot
        
        undergo mitosis
        
        grow into sporophyte
- - - - belong to Cooksonia
        
        had upright stems
        
        that were simple, short cylinders
        
        with no leaves
        
        had equal dichotomous branching
        
        both branches of equal
        
        size
        
        vigor
        
        had epidermis with
        
        a cuticle, cortex of parenchyma
        
        and a simple bundle
        
        of xylem composed of
        
        tracheids with annular secondary walls
        
        ends of branches
        
        were swollen and contained
        
        large, multicellular masses of sporogenous tissue
        
        surrounded by several layers of
        
        sterile cells
        
        were homosporous
        
        no seperate
        
        microspores and megespores
    - - two types of xylem organization
        
        in both
        
        the center is a
        
        solid mass of xylem
        
        with no pith
        
        called a protostele
        
        endarch protostele
        
        protoxylem located in the center
        
        xylem that differentiates while
        
        cells are small and narrow
        
        metaxylem differentiates on the
        
        outer edge of xylem mass
        
        differentiates after the cells have
        
        expanded and are larger
        
        exarch protostele
        
        metaxylem located in center
        
        of xylem mass
        
        protoxylem located on edges
        
        of as several groups
        
        next to the phloem
      - siphonostele
        
        pith present in center
        
        as occurs in ferns
        
        and seed plants
  - - - secondary growth
    - - to those of rhyniophytes
      - three characteristics makes us think
        
        they were distinct group
        
        sporangia were lateral
        
        not terminal
        
        as seen in lycophytes
        
        may represent line of evolution
        
        based on Zosterophyllum-like ancestors
        
        sporangia opened transversely along
        
        top edge
        
        xylem was an
        
        exarch protostele
    - - all are extinct
      - grew as small bunches
      - upper portions of stems
        
        had cuticle
        
        and stomata
      - stems were naked
        
        branched dichotomously
        
        contained small amount of
        
        xylem that consisted of
        
        tracheids with annular and
        
        scalariform secondary walls
        
        sporangial walls
        
        several layers thick
      - homosporous
- - - - genera Drepanophycus and Baragwanathia
        
        similar to presumed ancestors
        
        the zosterophyllophytes
        
        with an important difference
        
        enations were large
        
        and contained
        
        single well-developed trace
        
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        must have increased photosynthesis
        
        could be called leaves
        
        called microphylls in
        
        division Lycophyta
    - - evolution of true roots
        
        allowed lycophyte sporophytes
        
        to anchor firmly
        
        absorb more efficiently
        
        grow to tremendous size
  - - - clustered together in compact groups
        
        called cones or strobili
        
        protect them
    - - others became heterosporous
        
        having microspores and megaspores
        
        germinates to give rise to
        
        microgametophytes and megagametophytes
        
        megaspores in some species
        
        was retained within sporophyll
        
        protected by thick walled
        
        cells of the sporangium
        
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    - - evolution of seeds
    - - of evolution distinct
        
        from seed plants
        
        but having convergent evolution
        
        in several characters
        
        leaves
        
        roots
        
        secondary growth
        
        almost seeds
  - - - common in forests
        
        from tropicals to artic
      - all living species small herbs
        
        with prostrate rhizomes
        
        have true roots and
        
        short upright branches
        
        microphylls spirally arranged
        
        on their stems
        
        secondary growth never occurs
        
        sporangia may be
        
        arranged in cones
        
        distributed along the shoots
        
        all are homosporous
        
        a plesiomorphic trait
        
        spores germinate
        
        grow into bisexual gametophytes
        
        that produces
        
        antheridia
        
        archegonia
        
        in some species
        
        green and photosynthetic
        
        in others
        
        subterranean and heterotrophic
        
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    - - less common in
        
        temperate North America
      - plants are smaller
        
        and easily overlooked
        
        or mistaken to be mosses
      - best known species
        
        resurrection plant
        
        curls up and turns brown
        
        when dry and appears dead
        
        but uncurls and regreens
        
        when moistened
      - has the apomorphic condition
        
        of being heterosporous
        
        megagametophyte develops inside
        
        megaspore wall
        
        megaspore is not retained
        
        on the sporophyte
        
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        microgametophyte develop
        
        within spore wall
        
        and consist of a single vegetative cell
        
        and an antheridium
        
        many flagellate sperms produced
        
        and then released
        
        as spore wall ruptures
      - can be distinguished from lycopodiums
        
        by small flap of tissue
        
        called ligule
        
        on upper surface of leaves
        
        simple structures
        
        unknown adaptive advantages
    - - genus of about
        
        60 species of small
        
        unusual plants called quillworts
      - grow in wet
        
        muddy areas that
        
        occasionally become dry
      - body consists of
        
        small corm-like stem
        
        has roots attached
        
        below and above leaves
      - are heterosporous
        
        almost every leaf contain sporangia
      - microphylls have ligules
      - weak cambial growth
        
        results in
        
        production of additional
        
        cortex parenchyma
        
        to the exterior
        
        and a type of
        
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- - - - proposed for three genera of extinct plants
        
        fossils strongly resemble those of
        
        rhyniophytes
        
        having
        
        terminal sporangia that dehisced laterally
        
        homosporous
        
        dichotomous branching
        
        endarch vascular cylinder of tracheids
        
        considered distinct advancement because
        
        trend of overtopping
        
        unequal branching
        
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        In some species
        
        lateral branches were arranged
        
        regular spiral phyllotaxy
  - - - of homoplasic structures called leaves
        
        leaves on gametophytes
        
        on vascular plants
        
        enations/microphylls of zosterophyllophytes
        
        megaphylls
        
        leaves that evolved from
        
        branch systems and
        
        are present in
        
        all seed plants
        
        ferns
        
        equisetophytes
        
        if branch system
        
        produced sporangia
        
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        telome theory
        
        telomes
        
        those of last dichotomy
        
        if all become aligned
        
        in one plane
        
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  - - - united by three synapomorphies
        
        roots have exarch system
        
        have megaphylls
        
        have 30-kilobase inversion
        
        in large single-copy region
        
        of their plastid DNA
      - contains two sister clades
        
        monilophytes
        
        many are known as ferns
        
        others called fern allies
        
        lignophytes
        
        the woody plants
  - - - consist of
        
        several genera of extinct species
        
        one genus, Equisetum
        
        15 extant species
        
        known as horsetails or scouring rushes
    - - all herbs with
        
        no secondary growth
      - aerial stems
        
        characteristic joined structure
        
        whorl of fused leaves
        
        at the nodes
        
        leaves are small
        
        single trace of vascular tissue
        
        small megaphylls
        
        arise from
        
        deep subterranean rhizomes
      - if branches are present
        
        alternate with the leaves
      - true roots present
        
        produced at rhizome's nodes
    - - stems
        
        pith located in center
      - protoxylem forms
        
        next to pith
        
        interior to metaxylem
        
        thus is endarch
      - stem elongation
        
        causes cells to
        
        be stretched and torn
        
        forming canals
      - cortex composed of
        
        large cells
        
        outer ones are chlorophyllous
        
        air canals may be
        
        located in outer cortex
      - epidermis contains
        
        stomatal pores
        
        guard cells
        
        large amounts of silica
    - - sporangia always occur in
        
        groups of five to ten
        
        located on sporangiophore
        
        umbrella shaped
        
        short stalk
        
        flat, shield shaped head
        
        where sporangia project
        
        always arranged in
        
        compact spirals
        
        forming a strobilus
      - homosporous
        
        strobilus occurs at
        
        tip of green photosynthetic shoot
        
        after spores released
        
        germinate in moist soil
        
        develop into small
        
        green gametophytes
        
        no vascular tissue
        
        no epidermis or stomata
        
        body is
        
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        either male or bisexual
        
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  - - - in almost any habitat
        
        but
        
        moist, shady forest and lakesides
        
        considered "typical" fern habitats
    - - perennial and herbaceous
      - none is woody
        
        but some do achieve
        
        size of small trees
    - - single axis
        
        either vertical shoot
        
        or horizontal rhizome
        
        bears both
        
        true roots and megaphyllous leaves
    - - endarch siphonstele
        
        at each node
        
        leaf trace diverges
        
        from siphonostele
        
        leaving small segment
        
        of vascular cylinder
        
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    - - most are
        
        many layers thick
      - only one cell thick
        
        in filmy ferns
      - upper layer of palisade parenchyma
      - lower region of spongy mesophyll
        
        sori
        
        cluster of sporangia
        
        where meiosis occurs
      - can be small or large
        
        but almost always
        
        compound with
        
        rachis and leaflets
        
        usually contain considerable
        
        amount of vascular tissue
      - in most are
        
        serve both photosynthetic
        
        and are sporophylls
    - - when spores germinate
        
        grow into small
        
        simple heart-shaped
        
        or ribbon-shaped
        
        photosynthetic gametophytes
        
        with unicellular rhizoids
        
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        each usually develops both
        
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