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Vascular plants without seeds (the mega-hull line of evolution:…
Vascular plants without seeds
early vascular plants
rhiniophytes
cooksonia
earliest vascular
equal dichotomous branching
homosporous
two types of organization in xylem in stems
zosterophyllaphytes
named after principal genus zosterophyllum
small herbs without secondary growth
all extinct
grew in small bunches
15 cm tall
grew in swampy marshy areas
the microphyll line of evolution: lycophytes
morphology
earliest members
drepanophycus
barawanathia
enations were large
heterospory
in many lycophytes sporangia are clustered together
cones
offer protection
precondition for evolution of seeds
extant genera
lycopodium is fairly common in forests
true roots upright branches
homosporous
salagenella
less common in north america
the mega-hull line of evolution: euphyllophytes
trimerophytes
proposed in 1968
three genera of extinct plants
trimerophyton
psilophyton
pertica
origin of megaphylls
three distinct types of homoplasic
leaves
leaves on gametophytes of nonvascular
nations of zosterophyllophytes and lycophytes
megaphylls
monilophytes
united by three synapomorphies
their roots have exarch xylem
they have megaphylls
they have a 30 kilo base inversion
equisetophytes
arthrophyta
several extinct plants
one genus
equisetum
horse tails, scouring rushes
ferns
dominate the earth at present
leptosporangiate ferns
12,000 species
the term, "vascular cryptogams"
ferns and fern allies
lack seeds their reproduction is hidden (crypto)
