Asteroxylon mackiei

Reconstruction of Asteroxylon mackieiThis is the reconstruction of the plant Asteroxylon mackiei made bij Kidston and Lang (1920).
The size of the plant could be up to 50 cm with a stem diameter up to 1 cm. It is the biggest plant in the Rhynie Chert.
The 'leaves' are scalelike like those of the clubmosses. The sporangia are attached laterally along the stem and for this reason the plant is considered to be a ancestor of the clubmosses.
The name Asteroxylon points to the star-shaped xylem.
The tracheids of this plant, reinforced with annular and spiral thickenings, are common. In most cases the cell structure of the softer parts is not present any more.
The cylindrical roots are also rather common.

Transverse section of a stem of Asteroxylon

Transverse section of the stem with stellate xylem. 1 = xylem strand of the stem;
2 = rootlet growing through the decaying stem; 3 = xylem strands going to the leaflets;
4 = decaying cells of the stem; 5 = epidermis with stomata (enlarge!);
6 = section through a leaflet with xylem strand. Find another leaflet! Width  of the photo 2 cm.

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Asteroxylon mackiei

Star-shaped xylem

Xylem and phloem

Tracheids with annular and spiral thickenings


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