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Vascular Plants without Seeds (Concepts (transformation theory (postulates…
Vascular Plants without Seeds
Concepts
dibiontic life cycle
each species has a multicellular gametophyte and sporophyte
monobiontic
having only one multicellular generation
interpolation hypothesis
postulates that a small sporophyte came into existence when a zygote germinates mitotically
transformation theory
postulates that after the dibiontic life cycle, gametophyte and sporophyte become larger and more complex
Early Vascular Plants
Rhyniophyte
equal dichotomous branching
both branches being equal size and vigor
Xylem Structure
protostele
solid mass xylem with no pith
endarch protostele
protoxylem is located in the center
metaxylem differentiates on the outer edge
exarch protostele
metaxylem located at the center
protoxylem on the edges
siphonostele
pith is present in the center
Zosterophyllophytes
small herbs without secondary growth
enations
outgrowths
Euphyllophytes
overtoping
unequal branching, one stem more vigorous
megaphylls
leaves that evolved from branch systems
telome theory
megaphyll evolution summary
telome
ultimate twigs
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