The trunk was topped with a plume of long, grass-like, microphyllous leaves,[5] so that the plant looked somewhat like a tall, forked bottle brush.

[2][6] The underground structures of arborescent lycophytes including Sigillaria and Lepidodendron are assigned under the form taxon, Stigmaria.

The lycopsids had rhizomes or shoot-like rhizomorphic axes, with lateral appendages attached from the circular scars, forming an underground network of branched rootlets.

These stigmarian rootlets branched dichotomously from the rhizomorphs similar to Isoetes, and spread throughout the coal swamp forest areas where the lycopods were commonly found.

[7] Sigillaria, like many ancient lycopods, had a relatively short life cycle - growing rapidly and reaching maturity in a few years.