The Carboniferous forerunners of the tiny club-moss were then great trees with dichotomously branching stems and crowded linear leaves, such as Lepidodendron (with its fruit cone called Lepidostrobus), Halonia, Lepidophloios and Sigillaria, the largest plants of the period, with trunks sometimes 5 ft.
In the genus Lepidophloios the leaf-cushions are more prominent than in Lepidodendron, and their greatest diameter is in the transverse direction; on the older stems the leaf-scar lies towards the lower side of the cushion.
Primary phloem can be recognized with certainty in favourable cases, the question of the formation of secondary phloem by the cambium is not yet fully cleared up. In the Lepidodendron fuliginosum of Williamson, shown by its leaf-bases to have been a Lepidophloios, the secondary wood is very irregular, and consists largely of parenchyma.
In Ulodendron the large circular, distichously arranged prints were supposed to have been formed by the pressure of the bases of sessile cones, though this interpretation of the scars is open to doubt, and it is now more probable that they bore deciduous vegetative branches; in the Halonial branches characteristic of the genus Lepidophloios the tubercles may perhaps mark the points of insertion of pedunculate strobili.
Bothrodendron still survives, but Lepidodendron, Lepidophloios, and the ribbed Sigillariae are the characteristic Lycopods.
In 1895 Professor Zeiller described several plants from the province of Rio Grande do Sul in South America (Map A, including a few typical members of the Glossopteris flora associated with a European species, Lepidophloios laricinus, one of the characteristic types of the Coal period, and with certain ferns resembling some species from European Permian rocks.