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Chapter 21: Vascular Plants Without Seeds - Coggle Diagram
Chapter 21: Vascular Plants Without Seeds
Early Vascular Plants
Rhyniophytes
had equal dichotomous branching, both branches being equal of size and vigor.
homosporous, meaning no separate microspores and megaspores
belong to Cooksonia, a genus of extinct plants
plants of Cooksonia had an epidermis with a cuticle, a cortex of parenchyma, and a simple bundle of xylem composed of tracheids with annular secondary walls.
Xylem structure of Early Vascular Plants
two types of xylem organization
in both, the center is a solid mass of xylem with no pith
in an endarch protostele, protoxylem is located in the center and metaxylem differentiates on the outer edge of the xylem
in an exarch protostele, metaxylem is located in the center of the xylem mass and protoxylem on the edges
Zosterophyllophytes
named after the principal genus Zosteroplyllophytes
their sporangia were lateral, not terminal; sporangia opened transversely along the top edge, and their xylem was an exarch protostele
several zosterophyllophytes had a smooth surface, but others had outgrowths called enations
The Microphyll Line of Evolution: Lycophytes
The earliest lycophytes were members of the genera Drepanophycus and Baragwanathia
enations in the in the division lycophyta are called microphylls
in many extinct or extant lycophytes sporangia are clustered together in compact groups called cones or strobili, which protect them
The Megaphyll Line of Evolution: Euphyllophytes
at least 3 distinct types of homoplasic structures called leaves occur in plants
1) leaves on gametophytes of nonvascular plants, 2) enations of zosterphyllophytes and lycophytes, and 3) megaphylls, leaves that evolved from branch systems
the euphyllophytes contains 2 sister clades
monilophytes
lignophytes
equisetophytes have been classified as division Arthrophyta
consist of several genera of extinct plants and one genus, Equisetum
reproductive structures in Equisetum are specialized; sporangia always occur in groups of 5 to 10 located on an umbrella-shaped sporangiophore
Ferns
contain 2 types of sporangia
the eusporangium is initiated when several surface cells undergo periclinal divisions
leptosporangia are initiated when a single surface cell divides periclinally and forms a small outward protrusion
Psilotum and Tmesipteris
these two small genera contain the simplest of all living vascular plants
the psilotum is unique among living vascular plants in that it has lost the capacity to make roots and leaves
