1. Life on Earth Kingdom Plantae Part III
“Ferns”
Boston fern

2. Two Life Cycle Stages of Ferns
GAMETOPHYTE
SPOROPHYTE
Pteridium (bracken fern)

3. Phylum: Moniliophyta
Subphylum: Pterophyta (typical ferns, including water ferns, tree ferns, and grape ferns)
Subphylum: Psilophyta (wisk ferns or psilophytes)
Subphylum: Sphenophyta (horsetails and scouring rushes)

4. Subphylum: Pteridophyta (“typical ferns”)
Plants with megaphyllous leaves (called fronds) with branched veins
Most species have no “stem” but a perennial rhizome
All species are homosporous except the “water ferns”
Some species produce dimorphic fronds (vegetative and reproductive fronds)

5. Fern Terminology
Pinna
Rachis

6. Osmunda (fertile and sterile fronds)

7. Frond Development
Fronds develop in a coiled fashion known as circinate vernation
Young, coiled fronds are called fiddleheads
Some ferns are edible at this stage

8. Fern Reproduction
Fern plants ( diploid sporophytes) produce spores by meiosis in sporangia
These sporangia develop in small clusters (called sori) on the underside of the pinnae (or on separate pinnae)
Some species produce a protective indusium partially covering the sorus

9. Fern Sporangia

10. Pinna with Sori (no indusium)
sorus

11. Fern Sori with Indusia

12. Frond with Sori and Indusia

13. Fern Sporangia with Annulus
Sporangia forcibly eject the spores with the action of the annulus and lip cells

14. Gametophyte Generation
Spores develop by mitosis into haploid, photosynthetic gametophytes
The gametophyte thallus usually produces male antheridia first, then female archegonia
Flagellated sperm fertilize egg cells and the zygote develops into the next sporophyte fern plant

15. Gametophyte Generation

16. Fern Antheridia

17. Young Sporophytes

18. Fern Life Cycle

19. Fern Diversity
Some tropical species are “tree ferns” and produce a erect stem (especially the Order Marattiales)
Many ferns are epiphytes
Some ferns are aquatic (floating)
These “water ferns” are heterosporous, while all other ferns are homosporous
Ferns are important economically as ornamentals

20. Platycerium

21. Pleopeltis polypoides “resurrection fern”

22. Water Ferns (Azolla)

23. Azolla from a Distance

24. Marsilea (another water fern)

25. Marsilea

26. Salvinia and Azolla

27. Tropical Tree Ferns (Marattiales)

28. Tree Fern

29. Tree Fern

30. Grape Ferns Ophioglossum and Botrychium

31. Botrychium

32. Subphylum: Psilophyta (wisk ferns)
Extant plants superficially similar to rhyniophytes, but now known to be “reduced” ferns
No true roots or leaves; homosporous
Erect “stem” and underground “rhizome” have protostele structure
Dichotomous branching common

33. Psilotum Psilotum (“wisk fern”)
produces trilobed sporangia on flaps of tissue called enations
previously viewed as a separate division, the Psilophyta

34. Psilotum

35. Tmesipteris (another Psilophyte from SE Asia and New Zealand)

36. Subphylum: Sphenophyta
Includes “horsetails” and “scouring rushes”
Only one extant genus: Equisteum
Characteristics:
hollow, jointed stems
microphyllous-like leaves
homosporous

37. Equisetum

38. Sheathing Leaves and Plants with Strobili

39. Equisetum (strobilus)

40. Equisetum (cont.) spores with two wall layers
outer wall is hygroscopic and humidity changes cause unwrapping of the 4 arms (elaters)
this action helps to break up the spore mass in spore dispersal

41. Equisetum spores and elaters