People who study wild plants collect specimens. Those collections are then preserved in museums called herbariums, mostly located at colleges and universities. They are then available for anyone who wants to study them. For example, the herbarium at the University of Michigan (http://lsa.umich.edu/herbarium/) has about 1.7 million specimens from around the world, with a strong emphasis on Michigan plants. Those specimens and ones at other herbaria were the basis for the three volumes of Michigan Flora, published between 1972 and 1985. Michigan Flora Online now gives us access to that information anytime, anywhere. It includes all that's been learned about Michigan plants since the original publications. 285 new species have been added, and more are coming. I have one now that I haven't yet sent in. Material from such specimens also supports the genetic studies now occurring. Those studies are enabling a much better understanding of plants and their relationships. Some of the 285 new Michigan species are plants now divided into two species, as with blue cohosh. The herbarium specimens are very carefully preserved, and last a long time. The oldest specimen from my home county is a bog birch collected in 1832. International herbaria go back even farther. One in Paris was started in 1635, and now has about 9 million specimens.