Wanderlust World Wanderlust World The pivotal development enabling terrestrial colonization was the evolution of vascular plants with desiccation-resistant adaptations during the Silurian Period (~444–416 Ma). Early bryophyte-grade plants (mosses, liverworts) colonized damp margins, but the innovation of vascular tissue (xylem/phloem) for internal water/nutrient transport and a waxy cuticle to prevent water loss allowed plants to grow upright, access sunlight, and survive in drier microsites. This created soils, oxygenated the atmosphere further, and provided food/habitat for arthropods (millipedes, arachnids) and later tetrapods. Without this botanical revolution, animal terrestrialization could not have occurred.