1. The Seedless Vascular Plants: Ferns and Their Relatives
Chapter 21

2. Outline Introduction Phylum Psilotophyta – The Whisk Ferns
Phylum Lycophyta – The Ground Pines, Spike Mosses and Quillworts
Phylum Equisetophyta – The Horsetails and Scouring Rushes
Phylum Polypodiophyta – The Ferns

3. Introduction During early stages of vascular plant evolution:
Internal conducting tissue developed
True leaves appeared
Roots functioning in absorption and anchorage developed
Gametophytes became progressively smaller
4 phyla of seedless vascular plants: Psilotophyta, Lycophyta, Equisetophyta, Polypodiophyta

4. Introduction Psilotophyta Sporophytes without true leaves or roots
Psilotum
Psilotophyta
Sporophytes without true leaves or roots
Stems and rhizomes fork evenly
Lycophyta
Plants covered with microphylls - leaves with single vein whose trace not associated with leaf gap
Lycopodium

5. Introduction Equisetophyta
Sporophytes with ribbed stems containing silica
Whorled, scalelike microphylls lacking chlorophyll
Polypodiophyta
Sporophytes with megaphylls - leaves with >1 vein and leaf trace associated with leaf gap
Often large and divided
Equisetum
A fern

6. Phylum Psilotophyta – The Whisk Ferns
Resemble small, green whisk brooms
Structure and form:
Sporophytes:
Dichotomously forking stems
Above ground stems arise from rhizomes
Lack leaves and roots

7. Phylum Psilotophyta – The Whisk Ferns
Structure and form cont’d.:
Sporophytes:
Enations - tiny, green, superficially leaflike, veinless, photosynthetic flaps of tissue
Roots, aided by mycorrhizal fungi, scattered along rhizomes

8. Phylum Psilotophyta – The Whisk Ferns
Reproduction:
Sporangia fused in 3s and produced at tips of short branches
Gametophytes develop from spores beneath ground
Branch dichotomously
No chlorophyll
Rhizoids aided by mycorrhizal fungi
Archegonia and antheridia scattered on surface
Zygote develops foot and rhizome
Rhizome separates from foot

9. Phylum Psilotophyta – The Whisk Ferns
Reproduction cont’d.:

10. Phylum Psilotophyta – The Whisk Ferns
Fossil whisk fern look-alikes
Silurian, 400 mya
Cooksonia and Rhynia
Naked stems and terminal sporangia
Devonian, mya
Zosterophyllum
Naked stems and rounded sporangia along stem
Thought to be ancestral to club mosses

11. Phylum Lycophyta – The Ground Pines, Spike Mosses, and Quillworts
Collectively called club mosses
2 living major genera
Lycopodium
Selaginella
2 living minor genera
Several genera became extinct about 270 mya
Sporophytes have microphylls
Have true roots and stems

12. Phylum Lycophyta Lycopodium - ground pines Often grow on forest floors
Stems simple or branched
Develop from branching rhizomes
Leaves usually < 1 cm long
Roots develop along rhizomes

13. Phylum Lycophyta Lycopodium reproduction:
Sporangia in axils of sporophylls - sporangium-bearing leaves
Some species have sporophylls with no chlorophyll, are smaller than other leaves and clustered into strobili (singular: strobus)
In sporangia, sporocytes undergo meiosis, producing spores

14. Phylum Lycophyta
Lycopodium reproduction cont’d.:
Gametophyte

15. Phylum Lycophyta Selaginella - spike mosses Abundant in tropics
Branch more freely than ground pines
Leaves with ligule on upper surface

16. Phylum Lycophyta Selaginella reproduction:
Produce 2 different kinds of gametophytes = heterospory
Microsporophylls bear microsporangia containing microsporocytes, producing tiny microspores - becomes male gametophyte, consisting of antheridium within microspore wall
Megasporophylls bear megasporangia containing megasporocytes, producing 4 large megaspores -develops into female gametophyte consisting of many cells inside megaspore
Several archegonia produced where spore wall ruptures

17. Phylum Lycophyta
Selaginella reproduction cont’d.:

18. Phylum Lycophyta Isoetes - quillworts
Found in areas partially submerged in H2O for part of year
Microphylls arranged in tight spiral on stubby stem
Ligules occur towards leaf bases
Corms have vascular cambium
Plants generally > 10 cm tall

19. Phylum Lycophyta Isoetes reproduction:
Similar to spike mosses, except no strobili
Sporangia at bases of leaves

20. Surface of Lepidodendron, showing microphyll bases
Phylum Lycophyta
Ancient relatives of club mosses and quillworts:
Dominant members of forests and swamps of Carboniferous, 325 mya
Large, tree-like, up to 30 meters tall - Lepidodendron
Surface of Lepidodendron, showing microphyll bases

21. Phylum Equisetophyta – The Horsetails and Scouring Rushes
Equisetum
Branched and unbranched forms, usually > 1.3 m tall
Stems jointed and ribbed
If branched, branches in whorls
Scalelike leaves in whorls at nodes
Stomata in grooves between ribs

22. Phylum Equisetophyta Stem anatomy:
Hollow central cavity from break down of pith
Two cylinders of smaller canals outside pith
Carinal canals - conduct H2O with xylem and phloem to outside
Vallecular canals - outside carinal canals contain air
Silica deposits on walls of stem epidermal cells

23. Phylum Equisetophyta

24. Phylum Equisetophyta Equisetum reproduction:
Asexual by fragmentation of rhizomes
Sexual reproduction:
Strobili at tips of stems with sporangia connected to sporangiophores
Spores green with 4 elaters attached
Gametophytes lobed, green, cushion-like, up to 8 mm in diameter
Spores with elaters

25. Phylum Equisetophyta
Equisetum reproduction cont’d.:

26. Reconstruction of fossil giant horsetail, Calamites
Phylum Equisetophyta
Ancient relatives of horsetails:
Flourished in Carboniferous, 300 mya
Human and ecological relevance:
Many giant horsetails used for food by humans and other animals
Scouring rush stems used for scouring and sharpening
Reconstruction of fossil giant horsetail, Calamites

27. Phylum Polypodiophyta – The Ferns
Structure and form:
Vary in size from tiny floating forms < 1 cm to giant tropical tree ferns up to 25 m tall
Fern leaves are megaphylls - fronds
Typically divided into smaller segments
Require external H2O for reproduction

28. Phylum Polypodiophyta – The Ferns
Reproduction:
Sporophyte conspicuous phase
Fronds, rhizomes, roots
Fronds first appear coiled in crozier, and unroll and expand
Fronds divided into segments called pinnae (singular: pinna)
Crozier

29. Phylum Polypodiophyta – The Ferns
Reproduction cont’d.:
Sporangia stalked
Scattered on lower leaf surface, confined to margins, or found in discrete clusters called sori (singular: sorus)
Sori may be protected by indusia (singular: indusium)
With row of heavy- walled, brownish cells = annulus
Sorus covered by indusium

30. Phylum Polypodiophyta – The Ferns
Reproduction cont’d.:
Meiosis forms spores in sporangia
Spores released and grow into gametophytes called prothalli (singular: prothallus)
Prothalli one cell thick, and have archegonia and antheridia
Zygote develops into young sporophyte
Gametophyte dies and leaves sporophyte growing independently

31. Phylum Polypodiophyta – The Ferns
Reproduction cont’d.:

32. Phylum Polypodiophyta – The Ferns
Fossil relatives of ferns:
Devonian, 375 mya - possible ancestors of ferns
Resemble ferns in growth habit, but look more like whisk ferns
Possible ancestors: Aglaophyton and Psilophyton

33. Phylum Polypodiophyta – The Ferns
Fossil relatives of ferns cont’d.
Carboniferous, mya - tree ferns abundant
Seeds found on some of fossil tree ferns

34. Phylum Polypodiophyta
Human and ecological relevance:
House plants
Function well as air filters
Outdoor ornamentals
Cooked rhizomes as food
Folk medicine
Fronds used in thatching for houses.
Basketry and weaving

35. Review Introduction Phylum Psilotophyta – The Whisk Ferns
Phylum Lycophyta – The Ground Pines, Spike Mosses and Quillworts
Phylum Equisetophyta – The Horsetails and Scouring Rushes
Phylum Polypodiophyta – The Ferns