What is a herbarium?
A herbarium is a collection preserved plant specimens (although many herbaria also include algae and fungi). Specimens can take many forms. For example, flowering plants are normally pressed, dried and mounted onto card whereas mosses are simply placed in a paper packet. Each specimen is accompanied by information on where and when it was collected, by whom, its correct botanical name, and sometimes information on associated species and ecological preferences.
The specimens are a primary source of information on the classification and distribution of plants, algae and fungi. These specimens are the working tools of scientists who contribute to our knowledge and understanding of biodiversity and conservation through the discovery, classification and description of new species.
Importance of Herbaria
An herbarium sheet is first, a preserved sample of the plant itself and second, an historical document. It is this latter aspect which is unique. Herbarium material provides a time-line and it is a time-line with a genetic component. Biological and evolutionary studies depend upon having collections that have genes, chemicals etc. and mostly these are derived from living material. The herbarium specimen is the only repository of historical genetic information.
This is illustrated by Cochlearia danica which shows a changing distribution of trichomes on the leaf surface. When plotted against concentration of carbon dioxide it is revealed that an increase in CO2 changes the distribution of trichomes. This is only possible to demonstrate using herbarium material collected over a significant period of time.
Follow this link for 100 uses of herbaria.