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Vascular Plants Without Seeds (Concepts (Interpolation Hypothesis…
Vascular Plants Without Seeds
Concepts
Dibiontic Life Cycle
each species has a multicellular gametophyte
also a multicellular sporophyte
Monobiontic
only one multicellular generation
zygotes only undergoes meiosis
Interpolation Hypothesis
postulates that a small sporophyte came into existence
when a zygote germinated mitotically instead of meiotically
Figure 21-1
Transformation Theory
after the dibiontic life cycle, both gametophyte and sporophyte became larger
more complex and vascularized
Figure 21-2
Early Vascular Plants
Rhyniophytes
Equal Dichotomous Branching
both branches being equal size and vigor
Rhyniophytes
fossils were the no separate microspores and megaspores
Figure 21-5
Xylem Structure of Early Vascular Plants
Protostele
center is a solid mass of xylem with no pith
Endarch Protostele
protoxylem is located in the center and metaxylem differentiates on the outer edge of the xylem mass
Exrach Protostele
metaxylem located in the center of the xylem mass
protoxylem located on the edges as several groups next to the phloem
Siphonostele
pith is present in the center
Zosterophyllophytes
small herbs without secondary growth.
Figure 21-8
Figure 21-10
Enations
increases the photosynthetic surface area of the plants
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The Microphyll Lie of Evolution: Lycophytes
Morphology
Microphylls
enations in the division
Heterspory
Cones
'Strobili"
sporangia are clustered together
Extant Genera
Ligule
upper surface of the
Selaginella
leaves
Figure 21-17
The Megaphyll Line of Evolution: Euphyllophytes
Trimerophytes
Overtopping
Pseudomopodial Branching
main trunk rather than a series of dichotomues
Origin of Megaphylls (Euphylls)
Megaphylls
leaves that evolved from branch systems and are present in all seed plants
Telome Theory
ultimate twigs
Sporophyll
sporangium-bearing, leaf-like structure
Euphyllophtes
megaphyllous plants form a monophyletic clade
Equisetophytes
Horsetails
"Scouring Rushes"
Sporangiophore
umbrella-shaped
Monopodial Growth
main trunk, lateral branches, true leaves and true roots
Ferns
Leptosporangiate Ferns
Leaf Trace
diverges from the siphonostele
Leaf Gap
small segment of the vascular cylinder as just parenchyma
Figure 21-29
