Networks of highly branched stigmarian rootlets developed on the first giant trees. Lycophyte trees were the tallest in the Carboniferous coal swamp forests. Their shoot and rooting (stigmarian) systems were modified leafy shoot systems, distinct from the roots of all other plants.

See the source article by following the link below:
Networks of highly branched stigmarian rootlets developed on the first giant trees. Lycophyte trees were the tallest in the Carboniferous coal swamp forests. Their shoot and rooting (stigmarian) systems were modified leafy shoot systems, distinct from the roots of all other plants.