Vascular Plants w/out seeds. (Megaphyll Evolution (Origin of Megaphylls (3…
Vascular Plants w/out seeds.
Early Vascular Plants
Earliest fossils that belonged to land plants were
, a genus of extinct plants.
Equal dichotomous branching
Epidermis with a cuticle
Simple bundle of Xylem
Ends of branches contained large masses
All plants that have the same characteristics as
are classified as Rhyniophytes.
were other early vascular plants similar to
They, of course, shared many similar characteristics.
Named after principal genus
Small herbs without secondary growth.
3 important distinctions
Sporangia opened transversely along top edge
Xylem was an exacrh protostele (protoxylem on outside, metaxylem in center).
Sporangia were lateral.
Some of the simplest vascular plants alive today may indeed represent a line of evolution based on
Many were similar to Rhyniophytes.
Easily mistaken to be mosses.
Best known species is the resurrection plant.
Curls up, turns brown, and appears dead upon drying. Uncurls and regreens when moistened.
Less common in temperate North America
May be distinguished by a small flap of tissue known as the ligule, located on the leaves.
Genus of about 60 species.
Mostly small, unusual plants called quillworts.
Growth occurs in wet, muddy areas that occasionally become dry.
Body consists of a corn-like stem with roots attached below and leaves above.
Microphylls also have ligules.
Very similar plants to
Several botanists seem to suggest that these are merely extreme forms of
is fairly common in forests from tropical to arctic regions.
200 living species
Small herbs with true roots and short, upright, branches.
Microphylls are spirally arranged on stems.
All species are homosporous.
Earliest lycophytes were members of the genera
Similar to their ancestors, zosterophyllophytes, with one major difference (below).
Enations were large, up to 4cm in length. It contained a single trace of vascular tissue.
May, technically, be called "leaves".
In reality, these are named microphylls for clarity.
Not the line of evolution that led to ferns and seed plants.
True roots evolved, allowing lycophyte sporophytes to anchor, absorb, and grow far more efficiently.
Extinct Lycophyte characteristics and names.
Wood was very similar to modern day pines.
Origin of Megaphylls
3 distinct types of homoplasic structures
Leaves on gametophytes of nonvascular plants
Evolved from branch systems and are present in all seed plants.
Evolution summed up as the telome theory
The leaves we see on trees are a result of around 300 million years of evolution.
By far the most common type of plant.
Many are ferns.
One of two sister clades under euphyllophytes
The other clade related is lignophytes
United by 3 synapomorphies
They have megaphylls.
They have a 30-kilobase inversion in the large single-copy region of their plastid DNA.
Roots have exarch xylem.
This division was proposed in 1968 for three genera of extinct plants (below).
Genera of extinct plants
Fossils strongly resemble rhyniophytes.
Became distinct during the Lower Divonian.
Unequal branching where one stem was more vigorous.
A single main trunk.
Small lateral branches, some fertile, bearing sporangia, and some sterile.
Classified as division Arthrophyta
Consist of several extinct plants and one genus.
15 extant species known as horsetails or scouring rushes.
The living plants have no secondary growth.
Usually less than 1 meter tall.
Reproductive structures are very specialized.