See Mabberley, D.J. in Taxon 53(1): 192. 2004 ('From the internal evidence, the parts making up vol. 1 were issued from 1805 until at least 1818, those for vol. 2 from 1805 until at least 1825'). Available online: https://books.google.co.uk/books?id=ZNpcdeWHg2sC&printsec=frontcover#v=onepage&q&f=false