The name of a plant species is attached to what is called the TYPE specimen. This is the specimen which was described by the author of the name and is the ultimate authority for the description and characteristics of the species, to which any doubtful specimens can be compared.
Type specimens are also designated for infra-specific taxa like subspecies, varietas and forma.
Cultivars did not have type specimens but ICPS is now offering possibilities to registrer each cultivar on a standard process which contains photograph and associated data to act as a standard reference for the cv. or hybrid name but no herbarium specimen is asked with. If you are interested, go here (- link - )
Examples of type specimen (click on the pictures to enlarge) :
Type specimen of Pinguicula gypsicola, from the NYBG New York Botanical Garden.
Type specimen of Pinguicula sodalium, species that was later renamed P. moranensis var. neovolcanica, from the NYBG New York Botanical Garden.