Classification of Pteridophytes by Smith (1955), Bold (1957) and Zimmerman (1959)

Pteridophytes are seedless vascular plants. In this post, we will summarize the classification proposed by Smith (1955), Bold( 1957) and Zimmerman (1959).
Pteridophytes classification by Smith

There are 4 divisions: 
1. Psilophyta 2. Lycophyta 3. Sphenophyta and 4. Pterophyta

1. Psilophyta:
Psilotum comes under psilophyta. Remember the characteristics of Psilotum. Look at the figure and that makes general characters of division Psilophyta
Psilotum nudum
• Most primitive
• Rootless with rhizoids
• Dichotomously branched photosynthetic stem
• Leaves often absent
• Protostele: is the condition where central core of xylem surrounded by phloem
• Homosporous Synangium: trilocular structure that encloses sporangia
• Eg: Fossil genera: Rhynia and Horneophyton
• Living genera Psilotum and Tmesipteris
2. Lycophyta (Club moss or spike moss)
• Differentiated plant body
• Microphyllous leaves
• Protostele sometimes siphonostele
• Sporophylls aggregate to form strobili or cones
• Both homosporous and heterosporous. Lycopodium is homosporous whereas  Selaginella is heterosporous
• Gametophyte depends on fungus for food
3. Sphenophyta (Horse tail)
• All are fossils except Equisetum
• Differentiated plant body
• Stem joined with nodes and internodes
• Scaly leaves seen as whorl around the node
• Sporangia forming strobili or cones
• Homosporous
4. Pterophya (Ferns or Filicophyta)
• Most widely distributed vascular cryptogams
• Differentiated plant body stem mostly rhizomatous
• Leaves macrophyllous called as fronds
• Young leaves show circinate vernation (spirally coiled)
• Stele: protostele, siphonostele or dictyostele
• Sporangia form sori on abaxial side of the leaf
• Sporocarp in Marselia
• Indusium may be true or false
• Homosporous (Pteris) or heterosporous( Marselia)
• Antherozoids multiflagellated
This is the summary of classification system of Pteridophytes. 
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