Underground part of a clubmoss tree in the Museum Am Schölerberg at Osnabrück.
The axes are not real roots but they can be considered as a kind of underground side branches of the trunk.
To these root bearers small real rootlets were attached. When these rootlets fell off characteristic little circular scars (stigmas) remained.
This explaines the name Stigmaria. The underground parts of Lepidodendron and Sigillaria cannot be distinguished in most cases.

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Stigmaria ficoides with scars and rootlets.
Ibbenbüren (Germ.), Westfalian B. Height of the photo 15 cm.

Stigmaria ficoides with rootlets.
Piesberg (Osnabrück, Germ.), Westfalian D. Height of the photo 40 cm.
Fossils of Stigmaria are frequently found in the root layer under the coal seam.

Stigmaria reticulata
with scars of the rootlets.
The strong wrinkling is characteristic for this species.
Duisburg-Hamborn, Westfalian A?
Height of the photo 6 cm
Coll. Arthur Reinink