Arrangement of the Herbarium
It is imperative that each of the 300,000 specimens in the collection can be reliably and immediately accessed and so slightly different systems are used for the different plant groups (algae, ferns flowering plants etc.). However, for all these groups the same basic principles apply: all material in a group is arranged according to an established system which places related material close together. The specimens are then further divided based on their geographic origin.
Some material remains unincorporated; often this consists of new collections or very difficult to identify older material; possibly, in both cases, comprising species new to science which, hence, cannot be identified until they are first described.