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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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