The Ferns

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The Ferns
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Spore dispersal


Siphonosteles

Megaphylls
the ferns

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fern morphology terminology

• ferns have megaphylls, commonly called fronds
• fern fronds typically have circinate vernation,
  expand by unrolling. Unexpanded fronds are often
  referred to as fiddleheads or croziers.
• in most ferns the stem is an underground
  rhizome, although in some groups it can be erect
  and stocky
• roots are adventitous and borne at the nodes
• sporangia are usually abaxial on fronds and
  occur in clusters called sori
• there are of two types of sporangia in the
  ferns
• EUSPORANGIA and LEPTOSPORANGIA

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More terminology and frond dissection
twice- pinnate
Petiole or stipe
simple (entire)
once-pinnate
pinnate
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Megaphyll
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Siphonostele with nonoverlapping leaf gaps
B
C
Siphonosteles with overlapping leaf gaps
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Eusporangia
Leptosporangia

• 
  
• Sporangia sessile or short-stalked
• 
  
• Large sporangia (gt 0.5 mm in diameter)
• 
  
• Sporangial walls several cells thick plus
  tapetum
• 
  
• Sporangia have no specialized dehiscence cells
• 
  
• Sporangia produce a large number of spores.
  

• Sporangia on long, slender stalks
• Small sporangia (lt 0.1 mm in diameter)
• Sporangial walls that are 1 cell thick plus
  tapetum
• Sporangia usually have an annulus
• Sporangia produce relatively few spores
• (commonly 64)

Polypodiales
Ophioglossales Marattiales
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The Marattiales, an order of eusporangiate ferns
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Vegetative morphology of the Marattiales

• most species have short, upright, unbranched
  stems
• large pinnately compound leaves
• conspicuous swellings called pulvini occur at the
  bases of pinnae in many species
• two persistent, clasping stipules occur at each
  leaf base
• shoot borne roots are large, fleshy, and smooth

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Members of the Marattiales have polycyclic
siphonosteles
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Reproductive morphology of the Marattiales

• eusporangia are abaxial on the leaf in two rows
  along veins
• eusporangia may be separate, unfused
  (Angiopteris spp.) or fused into a synangium
  (Marattia spp., Danaea spp.)

separate, unfused eusporangia
eusporangia fused into a synangium

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Psaronius, a marattialean fern of the Late
Carboniferous, had obconical stems
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Psaronius stems were clothed with a massive
mantle of adventitous roots for stability
Section from distal end of stem below
Lower stem section with substantial root mantle
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The Polypodiales, leptosporangiate ferns
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Spore dispersal


Eusporangium leptosporangium

Megaphylls

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174 simple or entire 165 lobed 170
pinnatifid 166 171 pinnatisect 167
pinnate 159 bipinnate 162 bipinnatifid
Examples of variously divided leaves
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Siphonostele with nonoverlapping leaf gaps
Siphonosteles with overlapping leaf gaps
B
C
dictyosteles
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A dictyostele is the most specialized type of
siphonostele seen in the Polypodiales
Leaf gaps
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