Thus the roots of Sigillaria are called Stigmaria, detached leaves Sigillariophyllum, and the fructifications Sigillariostrobus; the name Sigillaria applies to the stem, which, however, when old and partly decorticated has been called Syringodendron, while its woody cylinder has often been described under the name Diploxylon.
The roots of several of these forms are known as Stigmaria.
For example, the form and structure of Stigmaria have long been well known; but it is seldom possible to determine whether a given Stigmaria belonged to Sigillaria, Lepidodendron or some other genus.
To these, underground organs the name Stigmaria is applied; they are not clearly distinguishable from the corresponding parts of Sigillaria.
These organs, to which the name Stigmaria was given by Brongniart, have been found in connexion with the upright stems both of Sigillaria and Lepidodendron.