Gymnosperm the genome of "Picea abies" in 2013. Gymnosperm The gymnosperms , also known as Acrogymnospermae, are a group of seed-producing plants that includes conifers, cycads, "Ginkgo", and gnetophytes. The term "gymnosperm" comes from the Greek composite word "γυμνόσπερμος" (γυμνός gymnos, "naked" and σπέρμα sperma, "seed"), meaning "naked seeds". The name is based on the unenclosed condition of their seeds (called ovules in their unfertilized state). The non-encased condition of their seeds stands in contrast to the seeds and ovules of flowering plants (angiosperms), which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves,
Evolutionary history of plants they were too scarce to impact the atmospheric composition until around . These organisms, although phylogenetically diverse, were probably small and simple, forming little more than an algal scum. However, evidence of the earliest land plants occurs much later at about 470Ma, in lower middle Ordovician rocks from Saudi Arabia and Gondwana in the form of spores with decay-resistant walls. These spores, known as cryptospores, were produced either singly (monads), in pairs (dyads) or groups of four (tetrads), and their microstructure resembles that of modern liverwort spores, suggesting they share an equivalent grade of organisation. Their walls contain sporopollenin –