Seedless vascular plants continued Chapter 17 Phylum Pteridophyta

Seedless vascular plants continued

Chapter 17

Phylum Pteridophyta

• Majority of Pteridophyta are ferns

• Most living ferns are homosporous

• Two kinds of sporangia in ferns

• Eusporangium

• Large and contain many spores

• Multicellular in origin

• Leptosporangia

• Arise from a single cell

• Tapetum is two-cells-thick nutritive tissue

• Annulus drying results in catapult-like discharge of spores

Pteridophyta

• Eusporate ferns

• Ophioglossales and Marattiales

• Homosporous leptosporangiate ferns

• Filicales

• Heterosporous leptosporangiate ferns

• Marsileales and Salviniales (water ferns)

• Whisk ferns (Eusporate and rootless)

• Psilotales

Order Ophioglossales

• 3 genera (Botrychium, Ophioglossum)

• Each leaf has a vegetative portion or blade and a fertile segment

• Gametophytes are subterranean, tuberous, elongate and have endophytic fungi

• Gametophytes resemble those of Psilotales

Marattiales

• Look more like “ferns”

• Six living genera of 200 species

Filicales

• Homosporous leptosporangiate

• 10,500 species

• Fronds are megaphylls of sporophyte

• Fronds are divided into pinnae along rachis

• Fiddleheads – circinate vernation leaf development

• Sporophyte is perennial stage in ferns

Filicales

• Sporangia occur in clusters called sori in many genera

Filicales

• Young sori may be covered by specialized outgrowths of leaves called indusia

Filicales

• Bisexual gametophyte is heart-shaped prothallus with rhizoids

• 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

• Heterosporous leptosporangiate ferns

• Marsilcales and Salviniales

Water ferns

• Sporocarps resist drying

• Azolla contains cynanobacteria

Psilotales

• Whisk ferns with two genera, Psilotum and Tmesipteris

• Rootless and eusporangiate

• Bisexual subterranean gametophyte with a symbiotic fungus

Equisitales

• Genus Equisetum, horsetails

• Jointed stems and rough textures

• 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