||Rows of closely packed cells, rectangular in section.
Spore cases or conceptacles.
||Rows of closely packed cells with polygonal cross
sections. Cross partitions present though frequently very thin.
|Laminariales and others
||Corded strands of parallel threads. Frond types.
||Highly developed small bushy plants. Fossils usually
consist of calcified, heavily ribbed, spherical reproductive organs and
the whorled branches that bear them.
||A central stalk, preserved as a tube or bulb,
surrounded by tufts of leaves or leaf bases, preserved as knobs or
||Small tubes, loosely arranged so as to form segmented
stems. Tubes round in cross section and branching.
||Small tubes so loosely arranged as not to compress
each other. No cross partitions visible.
||Cellular structure rarely preserved. The lime is
deposited as crusts on the outside of the colony or cell, or between the
tissues, not in the cell wall. Classified on the basis of growth habit
and form of colony.
|No known fossils