File:Ephedra (Mormon tea) (Arches National Park, Utah, USA) 3 (15768813772).jpg

Ephedra - Mormon tea in Utah, USA.

Plants are multicellular, photosynthesizing eucaryotes. Most species occupy terrestrial environments, but they also occur in freshwater and saltwater aquatic environments. The oldest known land plants in the fossil record are Ordovician to Silurian. Land plant body fossils are known in Silurian sedimentary rocks - they are small and simple plants (e.g., Cooksonia). Fossil root traces in paleosol horizons are known in the Ordovician. During the Devonian, the first trees and forests appeared. Earth's initial forestation event occurred during the Middle to Late Paleozoic. Earth's continents have been partly to mostly covered with forests ever since the Late Devonian. Occasional mass extinction events temporarily removed much of Earth's plant ecosystems - this occurred at the Permian-Triassic boundary (251 million years ago) and the Cretaceous-Tertiary boundary (65 million years ago).

The most conspicuous group of living plants is the angiosperms, the flowering plants. They first unambiguously appeared in the fossil record during the Cretaceous. They quickly dominated Earth's terrestrial ecosystems, and have dominated ever since. This domination was due to the evolutionary success of flowers, which are structures that greatly aid angiosperm reproduction.

Ephedra (see above photo) is one of a few plants that defies traditional plant classification. Botanists generally consider it to be an odd gymnosperm or “transitional” between gymnosperms and angiosperms. The high-level taxon “Chlamydospermae” has been established for this and a few other forms. Ephedra is a medium-sized shrub having many stiff, upright to semi-upright, essentially bare branches with regularly spaced nodes. Tiny and scale-like leaves occur at the nodes along the branches. There are between 30 and 40 living species of Ephedra. Species identification generally requires very close examination. It prefers pebbly or sandy soil in cool desert settings. Ephedra is known from many desert environments in the New Wold and much of the Old World.

Classification: Plantae, Chlamydospermae, Gnetales

Locality: Park Avenue, Arches National Park, eastern Utah, USA.

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