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  • Equisetum cone ls x12. Umbrella-shaped sporangium bearing structures with sporangia pointed back toward the cone axis are a major characteristic of the sphenopsids. These sporangium bearing structures are called sporangiophores. Equisetum cones are homosporous (make only one kind of spore).
  • Equisetum sporangiophore x40, seen in a cone ls. The cone axis is on the right.
  • Equisetum gametophyte x20. These free living plants are capable of photosynthesis. Sperm bearing antheridia and egg bearing archegonia can be seen on the upper surface.
  • Equisetum young antheridium x400. This is on a gametophyte. Each of the central cells will undergo meiosis to produce 4 sperm.
  • Equisetum arvense stem xs x20.
  • Equisetum arvense shoot apex x100 showing leaf primordia and the triangular shaped apical cell that caps the apical meristem.
  • Sphenophyllum stem xs x12. This is a Pennsylvanian-age petrified fossil sphenopsid stem. The specimen was obtained from a coal seam in southeastern Kansas.
  • Calmites stem and leaves xs x20. This is another Pennsylvanian-age petrified fossil sphenopsid stem. The specimen is from a coal seam in Illinois.

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