The Carboniferous arborescent lycopods were the largest and most specialized members of this group, having developed from the simpler Devonian forms described asLepidodendropsis. The changes of external morphology and internal anatomy show that the plants belonging to the Lepidodendraceae had determinate growth patterns. Mature trees had tall trunks with crowns of dichotomously branched shoots. Their shallow, dichotomizing rooting systems are rhizophores calledStigmaria. The plants were heterosporous, having terminal cones on their ultimate branches. These cones are either included within the Lepidodendraceae, or referred to the Lepidocarpaceae if they possessed only one functional megaspore within each megasporangium. The Lepidocarpaceae therefore is a family of megasporangiate cones which were most probably borne on shoots belonging to the Lepidodendraceae. The two families were most common in the Upper Carboniferous of the equatorial Euramerican province, although they also lived in the Cathaysian flora of China and Southeast Asia. Plant compression and dispersed spore assemblages indicate that the Lepidodendraceae grew in the coal basin swamps although in more than one type of plant community.