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Vascular Plants Without Seeds (The Megaphyll Line of Evolution:…
Vascular Plants Without Seeds
Early Vascular Plants
Rhyniophytes
Earliest vascular land plant fossil belong to Cooksonia (extinct)
Equal dichotomous branching
Only central cells are sporogenous
Homosporous
Xylem Structure of Early Vascular Plants
Two typs of xylem organization, which both had a protostele
Endarch protostele
Exarch protostele
Zosterophyllophytes
Small herbs without secondary growth
3 distinct characteristics differentiate it from Rhyniophytes
Sporangia were lateral, not terminal
Sporangia open tranversely along the top edge
Xylem was an exarch protostele
Small brunches approximately 15 cm high
Enations
The Microphyll Line of Evolution: Lycophytes
Morphology
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Differentiated from Zosterophyllophytes with larger enations
Larger enations means more photosynthetic activity
Evolution of true roots
Some lycophytes had a vascular cambium and secondary growth
Heterospory
Sporangia are clustered together in groups called: cones or strobili
Lycophytes are unique because they have evidence of convergent evolution in several areas, but maintain their distinct characteristics still
Extant Genera
Lycopodium is fairly common in forests from many biomes
Selaginella is smaller and easily overlook and mistaken for lycompodium
Distinguished from Lycopodium by presence of the ligule
Isoetes or quillworts grow in wet, muddy areas with arid fluctuation
The Megaphyll Line of Evolution: Euphyllophytes
Trimerophytes
Three genera of extinct plants: Trimerophyton, Psilophyton, and Pertica
Fossils strongly resemble those of rhyniophytes
Overtopping: unequeal branching in which one stem is more vigorous than the others.
Pseudomonopodial branching: a single main trunk rather than a series of dichotomies
Origin of Megaphylls (Euphylls)
Megaphylls are leaves that evolved from branch systems
Telome theory
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Telomes
Planation
Webbing
https://www.youtube.com/watch?v=dH2e7Nam-D4
Monilophytes
One of two sister clades, along with the woody plants lignophytes
Ferns
Equisetophytes
A division of Arthrophyta.
Horestails or Scouring rushes
May attain a hieght of up to 10 m, but are usually less than 1 m tall.
Small leaves with a single trace of vascular tissue
Monopodial growth
Has a vascular cambium that developed separately of the lycophytes
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