Gymnosperms encompass a broad range of extant seed-producing plants. Their past diversity was much greater than the current 13 or 14 families, especially during the Mesozoic Era when they dominated the global flora. The ancient counterparts of the current Gymnosperms were keystone taxa of late Paleozoic and Mesozoic terrestrial ecosystems and were major contributors of organic matter to coals formed in those eras.
The name Gymnosperms comes from the Greek words "gymnos", which means naked; and "sperma", which means seed. Gymnosperms are phanerogams or spermatophytes without ovary and fruit. Their seeds or ovules are naked or exposed, without a fruit wall.They are therefore considered as fruitless flowering plants. Gymnosperm seeds develop either on the surface of scale- or leaf-like appendages or cones, or at the end of short stalks (Ginkgo).
All fossil and extant gymnosperms have some degree of secondary tissue production in their axes resulting in a woody stem. Some groups, such as cycads, produce only a small amount of secondary wood and retain a large central spongy pith - a condition called manoxylic wood. |
