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Vascular Plants Without Seeds (The Microphyll Line of Evolution:…
Vascular Plants Without Seeds
Early Vascular Plants
Rhyniophytes
Xylem Structure of Early Vascular Plants
protostele; solid mass of xylem with no pith
Endarch Protostele; protoxylem is located in the center and metaxylem differs on the outside
Exarch protostele; metaxylem in the center of the xylem mass and protoxylem on the edges
Siphonostele; pith is present in center (occurs in ferns and seed plants)
General Characteristics
equal dichotomous branching
upright simple stems
short cylinders w/ no leaves
made up of xylem, tracheids and secondary walls
includes Rhynia, Aglaophyton, and cooksonia (above)
Zosterophyllophytes
small herbs w/out secondary growth
Characteristics that differ from Rhyniophytes
sporangia open transversely
xylem is an exarch protostele
lateral sporangia
swampy areas
grow as small bunches (15cm)
The Microphyll Line of Evolution: Lycophytes
Heterospory
clustered together in cones or strobili
this is important to the development of seeds
almost had seeds
Morphology
How they differ from their close ancesotors, Zosterophyllophytes
large enations (4cm)
single, well-developed trace of vascular tissue
do not technically have "leaves" but they have microphylls
evolution of true roots; anchor firmly
had vascular cambium and secondary health
Extant Genera
ground pine or club moss
200 species
The Microphyll Line of Evolution: Euphyllophytes
Monilophytes
united by three synapomorphies
roots have exarch xylem
megaohylls
30-kilobase inversion in their DNA
Ferns
first seen in the devonian period
12,000 species (Leptosporangiate Ferns)
leaf trace diverges from the siphonostele
can be found in almost any habitat
leaves can be leathery or delicate; one cell thick in some but mostly thick layers
Eusporangia; Initiated when several surface cells undergo periclinal divisions; small multilayered plate of cells
Leptosporangia; initiated when sinlge surfaces cell dividespericlinally and forms smalll outward protrusions
Origins of Megaphylls
three distinct types of homoplasic structure
enactions/ microphylls of zosterophyllophytes
megaphylls
leaves that evolved from branch stems; telome theory
telomes; twigs
leaves on gametophytes of nonvascular plants
Equisetophytes
division Arthrophyta
several extinct with 15 extant; horsetails being one of them
usually less than 1m tall
joint structure; fused leaves and nodes; true roots
umbrella shaped sporangiophore
Trimerophytes
they resemble Rhyniophytes
over-topping;unequal branching
pseudomonopodial brancing; single main trunk
The Term "Vascular Cryptogams"
this name indicates that they( ferns and fern allies) have vascular tissue; they lack seed so their reproduction is hidden
