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Life on Earth Kingdom Plantae Part III. “Ferns”. Boston fern. GAMETOPHYTE. SPOROPHYTE. Pteridium (bracken fern). Two Life Cycle Stages of Ferns. Phylum: Moniliophyta. Subphylum: Pterophyta (typical ferns, including water ferns, tree ferns, and grape ferns)
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Life on EarthKingdom PlantaePart III “Ferns” Boston fern
GAMETOPHYTE SPOROPHYTE Pteridium(bracken fern) Two Life Cycle Stages of Ferns
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)
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)
Fern Terminology Pinna Rachis
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
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
Fern Sporangia with Annulus Sporangia forcibly eject the spores with the action of the annulus and lip cells
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
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
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
Psilotum (“wiskfern”) produces trilobed sporangia on flaps of tissue called enations previously viewed as a separate division, the Psilophyta Psilotum
Subphylum: Sphenophyta • Includes “horsetails” and “scouring rushes” • Only one extant genus: Equisteum • Characteristics: • hollow, jointed stems • microphyllous-like leaves • homosporous
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