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Vascular plants without seeds (Euphyllophytes (Monilophytes (United by 3…
Vascular plants without seeds
Lycophytes
Heterospory
Many are homosporous, some are heterosporous
Megaspore developed into a megagametophyte without enlarging
Sporangia are clustered together in compact groups called cones an strobili
Extant Genera
Approximately 200 species are herbs with prostate rhizomes
Selaginella is less common in temperate North America
Lycopodium is fairy common in forests
Morphology
Similar to the presumed ancestors, the Zostreophllophytes
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Enations in the division are called microphylls
Members of the genera Drepanophycus and Baagwanathia
Euphyllophytes
Monilophytes
Many Monilophytes are plants we know as fern
The Euphyllophytes contain 2 sister clades, the monilophytes and the woody plants
United by 3 Synapomorphies
They have megaphylls
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30-kilobase inversion in large single region of DNA
Their roots have exarch xylem
Equisetophytes
Consist of several genera of extinct plants. eg- Horsetail
Living plants are herbs without any secondary growth
Classified as Arthrophyta, also called Sphenophyta
Origin of Megaphylls
All subdivisions of a lateral branch become aligned in one plane
Sporangium bearing, leaf like structure is present
3 distinct types of homoplasic structure
Timerophytes
Has unequal branching, one stem was more vigorous
Became distinct from rhyniophytes during lower Devonian and existed until upper Devonian
Proposed in 1968 for 3 genera of extinct plants
Psilophyton
Pertica
Timerophyton
Ferns
Found in almost all habitat, moist, shady and lakeside are most common place
Fern sporophyte consist of single axis. either vertical shoot or horizontal rhizome
Early ferns first appeared in Devonian period and diversified greatly
Early vascular plants
Zosterophyllophytes
Zosterophyllum
All extinct
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Rebuchia
Asteroxylon
Enation
Crenatacaulis
Rhyniophytes
Equal dichotomes branching
Cooksonia
Aglaophyton
Rhynia
Xylem structure
Exarch protostele
Endarch protostele
Protostele
Siphnostele
Molecular study of evolution
Plants like mosses, liverworts, lycopods are simple and don't have much to compare
DNA restriction enzymes are used to analyze the order of genes
Vascular plants come from the Silurian period
Stems have a pith and there are siphonosteles not Protostele
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