C.P. numbers are often confused with collection numbers when in fact, C.P. stands for Ceylon Plants.

The numbers are listed in G.H.K. Thwaites' Enumeratio plantarum Zeylaniae, an enumeration of Ceylon plants, with descriptions of the new and little known genera and species, observations on their habitats, uses, native names, etc. (assisted in the identification of the species and synonymy by J.D. Hooker). Biodiversity Heritage Library

"Thwaites gave the same C.P. number to all specimens in the Herbarium which he considered to be of the same species, regardless of when or by whom they were collected. Consequently specimens which bear the same C.P. number may or may not actually be duplicates. " National Herbarium Sri Lanka

Therefore, do not enter C.P. numbers in HerbCat – the exception is if there is little other information, then enter this information in General Comments.