Wallich compiled and printed his Catalogue, a few pages at a time, during a five- and a two-year period spanning over two decades. Although the basis of his arrangement was established at the start, Wallich was not always consistent and introduced duplications and ambiguities throughout the Catalogue. He had set out to number and name Entries, with associated numbered Collections. Entries would consist of the taxon name and related information, and Collections would specify details such as the names of collectors, localities and dates. But in the process, when Wallich listed only one collection for a species, he often only numbered the Entry and neglected to number the Collection separately. We assume this was because Wallich intended the Catalogue pages to serve as labels for herbarium specimens, and not as a permanent reference. However, such inconcistencies  became a bigger issue later on during the distribution, when Wallich's system became much more intricate. For example, many new Collections were introduced as Addenda to be listed under Entries that had already been printed with single collections, which led to obscurities and complicated the interpretation of Wallich's numbering.

In order to unambiguously refer to elements within the Wallich Catalogue, it has been necessary to clarify these occurrences and establish an unambiguous numbering convention for Collections and Addenda in the Wallich Catalogue. We refer to this convention as as the ‘Edinburgh Notation’. The Edinburgh Notation has been devised by Mark Watson and Heleen Plaisier at Royal Botanic Garden Edinburgh, and was refined through the preparation of the Wallich Catalogue Online. Square brackets, ‘[’ and ‘]’, are used to mark any data that has been added to Wallich’s original.