Vascular Plants Without Seeds

Early Vascular Plants

Rhyniophytes

Zosterophyllophytes

The Microphyll Line of Evolution: Lycophytes

The Microphyll Line of Evolution: Euphyllophytes

Monilophytes

Ferns

Origins of Megaphylls

Equisetophytes

Trimerophytes

The Term "Vascular Cryptogams"

Heterospory

Morphology

Extant Genera

Xylem Structure of Early Vascular Plants

General Characteristics

equal dichotomous branching

upright simple stems

short cylinders w/ no leaves

made up of xylem, tracheids and secondary walls

image

includes Rhynia, Aglaophyton, and cooksonia (above)

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)

small herbs w/out secondary growth

Characteristics that differ from Rhyniophytes

sporangia open transversely

xylem is an exarch protostele

lateral sporangia

grow as small bunches (15cm)

swampy areas

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

image

clustered together in cones or strobili

this is important to the development of seeds

almost had seeds

ground pine or club moss

200 species

they resemble Rhyniophytes

over-topping;unequal branching

pseudomonopodial brancing; single main trunk

image

three distinct types of homoplasic structure

enactions/ microphylls of zosterophyllophytes

megaphylls

leaves on gametophytes of nonvascular plants

leaves that evolved from branch stems; telome theory

telomes; twigs

united by three synapomorphies

roots have exarch xylem

megaohylls

30-kilobase inversion in their DNA

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

image

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

image

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

this name indicates that they( ferns and fern allies) have vascular tissue; they lack seed so their reproduction is hidden