The unifacial cambium allowed plants to grow as tall as 50 metres.
Lacking secondary phloem, unifacial cambium plants developed alternative strategies to long range nutrient transport.
Xylem tissue in unifacial cambium plants was particularly structurally efficient.
Additional structural support was provided in lycophytes by a special periderm tissue in the outer cortex.
These trees appear to have lived for most of their life cycle as a 'stump', establishing root networks underground, before shooting up rapidly, releasing spores, and dying shortly thereafter.