FERNS & MOSSES
Seedless plants
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Spore-dispersed plants
• Seedless, dispersion by spores
• Advantages of spores
– Cheap, each one small, requires small resource
investment
– Produced in huge numbers
• Can result in huge numbers of offspring
• Disadvantage
– Wasteful, most spores unsuccessful
– Must land on good moist soil
– Little resource to support growing gametophyte
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Spore-dispersed vascular plants
• Vascular tissues, = xylem, phloem
– Allow growth to large size
– Local ferns, horsetails, club mosses not very
large, fronds 30-40 cm
– Tree ferns (tropical) to 18 m tall w/ fronds 3 m
long
– Prehistoric club mosses tree-sized
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Phylum Pterophyta
(Ferns)
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Phylum Pterophyta (Ferns)
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Leafy fronds, usually compound
Fronds grow as “fiddleheads”
Sporangia in sori under fronds
One kind of spores only
– homosporous
• Gametophyte with both antheridia & archegonia
– Antheridia release sperm before archegonia
mature!
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Phylum Sphenophyta
("horsetails" or "scouring rushes")
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Hollow, segmented stems
Minute bristle-like gray-brown fronds
Sporangia at tips of stems in strobilus
Heterosporous, two kinds of spores
– separate male & female gametophytes.
• Stems hard, gritty with crystals of silica
(SiO2, sand, glass)
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Phylum
Sphenophyta
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Phylum Lycophyta
("club mosses" or "ground pine")
• Short stems with microphylls,
– one vein per leaf (veins don’t branch)
• Sporangia at tips of stems or axils of fronds in
strobilus
• Heterosporous, two kinds of spores
– separate male & female gametophytes.
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Phylum Lycophyta
("club mosses" or "ground pine")
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Spore-dispersed nonvascular
plants
• Lack xylem or phloem
– Limited ability to transport water, minerals,
sugars
• Usually live in moist places
– Some can endure drying, metabolism
ceases until they are wet again.
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Phylum Bryophyta
(Mosses)
• Familiar, low green
soft masses on ground,
usually in moist places
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Phylum Bryophyta
(Mosses)
• Life Cycle (very different from ferns, etc.)
– dominant GAMETOPHYTE (haploid)
• familiar form
• green, with tiny leaf-like blades,
– antheridia & archegonia at top of moss
– zygote grows into SPOROPHYTE (diploid)
• = stalk + capsule
– Capsule dries, splits open, releases spores
– Spores grow into GAMETOPHYTE
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Moss Life Cycle
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Economic uses of ferns, mosses
• Horticulture, landscaping
• Peat moss (Sphagnum)
– soil conditioner, holds moisture,
– cut, dried, burned as fuel in Ireland,
Scandinavia.
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Formation of a peat bog
• Continental glacier plows up soil
• Glacier breaks up as it melts back
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Formation of a peat bog
• Hole left fills with meltwater
• Sphagnum grows from edges, may
eventually fill bog
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Economic uses of ferns, mosses
• Carboniferous Period (middle
Paleozoic)
– Ferns, tree ferns, tree-like
"horsetails," tree-like
lycophytes fossilized
– Coal deposits
– Power for heavy industry,
electrical generation
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Origins of plants
• from some green algae
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multicellular
same photosynthetic pigments, chlorophyll a, b
store food as starch
cellulose cell walls
alternation of generations
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Evolution of plants
• One group includes
mosses
– dominant gametophyte
• 2nd group includes
ferns, seed plants
– Sporophyte dominant
– Vascular tissue
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Evolution of plants
• One group includes mosses, hornworts
– dominant gametophyte, non-vascular
• 2nd group includes ferns, seed plants
– dominant sporophyte, vascular tissue
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Challenges to terrestrial organisms
(& how plants meet the challenges):
• 1. Getting water, water transport to cells
– specialized vascular tissues
• 2. Evaporation, drying
– waxes, oils in "epidermis," close stomata
• 3. Gravity, need for support
– fluid pressure in vascular tissue;
– lignified xylem = wood
• 4. Rapid temperature changes
– evaporative cooling requires even more water!
– seasonal: drop leaves or close stomata
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