By Sid Perkins
The first undisputed fossil of an orchid part has enabled scientists to estimate that the prized flowers appeared on the botanical scene around 80 million years ago.
With more than 25,000 species, orchids are the largest and most diverse group of flowering plants. Although most are found in the tropics, orchids grow on every continent except Antarctica and in every habitat except deserts. Scientists have assessed genetic differences among a variety of orchid species to develop a family tree that includes five subgroups.