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Fern sorus x100. You can see
stalked sporangea, each with a row of thickened spring-like cells in
the sporangium wall called an annulus. When the annulus drys out and
contracts, the sporangium will rip open at the area indicated.
Cryptomarium falcatum sorus x30. Located on the lower
surface of a leaflet (pinnule), the sorus is protected from premature
drying by an indusium which covers the sproangia.
Gleichenia rhizome xs x20. Primary xylem is in the center surrounded by phloem and cortex.
Pteridium rhizome xs x12. Plates of xylem are each surrounded by phloem.
Fern gametophyte x12. The dark round structures are antheridia or archegonia.
Antheridium x400. This is
the gametophyte's male sex organ. Each has a single layer of cells
containing coiled sperm. Antheridia are located at the margins of or on
the lower center of gametophytes.
Fern archegonium x400.
These female sex organs are near the center of the lower gametophyte
surface. Each has a neck, a neck canal (both easily visible in the
illustration) and an egg at the base. Sperm swim down the neck canal
and fertilize the egg.
Fern gametophyte with young sporophyte
x12. The sporophyte grows from a fertilized egg in an archegonium on
the gametophyte. The first sporophyte leaf (shown) looks nothing like
the large compound leaves produced later by the sporophyte.
Angiopteris evecta x30. Sorus on the lower surface of a leaflet.
Cyathia furfuracea sorus on lower surface of leaflet, x30.
Hemitelia horrida sorus on lower surface of leaflet, x30.
Marattia sorus on lower leaflet surface, x30.
Azolla caroliniana x20. This is one of the few heterosporous
ferns. It is aquatic. The dark structures are called sporocarps. These
are aggregations of megaspores and microspores.
Scolecopteris x30. This is a petrified Pennsylvanian-age
fossil fern. You can see a cross section of a leaflet (pinnule) with
sporangia underneath. The specimen is from a southern Illinois coal
Botryopteris petiole xs x20. This is a petrified Pennsylvanian-age fossil fern from eastern Kentucky.
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