To avoid mixing and confusing collection details, specimens are usually identified by a sequence field numbers that link specimens with their field notes.
Specimens are usually referred to by a combination of the collector's name and number, e.g Jones 4567
Some collections, especially older ones, have collectors' names but no numbers; a few have neither a collector's name nor number.
The combination of a collector's name and number is not unique for all collectors, or in some instances even for a single collector, so in most case a unique accession number is added to the specimen when it is incorporated into the herbarium.