Sometimes several collections of a specimen are made from the same shrub, tree or population. These provide a range of material from which to make specimens and give an indication of the range of variability in a plant or population.
Duplicate specimens made from these collections are often distributed to other herbaria as gifts or exchange to help build up coverage of collections and to provide backup security for the scientific information should a major disaster befall the sending herbarium.
The list of herbaria that were sent duplicates assists botants in locating further material of specimens; this is especially important when locating and selecting Type specimens.