Seedless vascular plants continued
Chapter 17
Phylum Pteridophyta
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Majority of Pteridophyta are ferns
Most living ferns are homosporous
 Two kinds of sporangia in ferns
 Eusporangium
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Large and contain many spores
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Multicellular in origin
 Leptosporangia
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Arise from a single cell
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Tapetum is two-cells-thick nutritive tissue
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Annulus drying results in catapult-like discharge of spores
Pteridophyta
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Eusporate ferns
 Ophioglossales and Marattiales
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Homosporous leptosporangiate ferns
 Filicales
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Heterosporous leptosporangiate ferns
 Marsileales and Salviniales (water ferns)
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Whisk ferns (Eusporate and rootless)
 Psilotales
Order Ophioglossales
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3 genera ( Botrychium , Ophioglossum )
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Each leaf has a vegetative portion or blade and a fertile segment
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Gametophytes are subterranean, tuberous, elongate and have endophytic fungi
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Gametophytes resemble those of Psilotales
Marattiales
 Look more like “ferns”
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Six living genera of 200 species
Filicales
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Homosporous leptosporangiate
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10,500 species
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Fronds are megaphylls of sporophyte
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Fronds are divided into pinnae along rachis
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Fiddleheads – circinate vernation leaf development
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Sporophyte is perennial stage in ferns

Filicales
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Sporangia occur in clusters called sori in many genera
Filicales
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Young sori may be covered by specialized outgrowths of leaves called indusia
Filicales
 Bisexual gametophyte is heart-shaped prothallus with rhizoids
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
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Archegonia near notch in heart
Antheridia near rhizoids
Development timing deterimines inbreeding or outcrossing frequency
Filicales
 Gametophyte is short-lived
 In some Appalachian species, no sporophytes are formed
 Produce gemmae
Water ferns
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Heterosporous leptosporangiate ferns
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Marsilcales and Salviniales
Water ferns

Sporocarps resist drying

Azolla contains cynanobacteria
Psilotales
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Whisk ferns with two genera,
Rootless and eusporangiate
Psilotum and Tmesipteris
Bisexual subterranean gametophyte with a symbiotic fungus
Equisitales
 Genus Equisetum , horsetails
 Jointed stems and rough textures
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Homosporous
Sporangia are borne in groups of 5-10 along the margin of umbrella-like structures called sporangiophores, which are clustered into stroboli
 Green, free-living gametophytes are bisexual or male