| Erophila verna var. spathulata | GB, VC17 Surrey, Thames Ditton Cultivated | John Thomas Irvine Boswell-Syme | Augustin Ley | 1861 | BIRM |
+ | Misopates orontium | GB, VC17 Surrey, Thames Ditton | John Thomas Irvine Boswell-Syme | Botanical Society of London Charles Bailey John Ray Hardy John Thomas Irvine Boswell-Syme | 9/1851 | MANCH |
| Nymphoides peltata | GB, VC17 Surrey, Walton Bridge | John Thomas Irvine Boswell-Syme | Botanical Society of London Harold Stuart Thompson Thomas Clark | 7/1852 | BIRM |
| Carex hirta | GB, VC17 Surrey, Wandsworth | Daniel Cooper | Frederick Janson Hanbury John Thomas Irvine Boswell-Syme | 1837 | BM |
| Melilotus indicus | GB, VC17 Surrey, Wandsworth | John Thomas Irvine Boswell-Syme | John Thomas Irvine Boswell-Syme | 1853 | BON |
| Schoenoplectus lacustris x triqueter = S. x carinatus | GB, VC17 Surrey, Wandsworth | John Thomas Irvine Boswell-Syme | Botanical Society of London John Thomas Irvine Boswell-Syme | 9/1851 8/1853 | BON |
| Carex divulsa | GB, VC17 Surrey, West Molesey | Hewett Cottrell Watson | John Thomas Irvine Boswell-Syme | 1866 | BM |
| Carex spicata | GB, VC17 Surrey, West Molesey | Hewett Cottrell Watson | John Thomas Irvine Boswell-Syme | 1866 | BM |
| Carex vulpina | GB, VC17 Surrey, West Molesey | Hewett Cottrell Watson | John Thomas Irvine Boswell-Syme Frederick Janson Hanbury Hewett Cottrell Watson | | BM |
| Carex elongata | GB, VC17 Surrey, Weybridge | Hewett Cottrell Watson | John Thomas Irvine Boswell-Syme Frederick Janson Hanbury | 6/1844 | BM |
| Carex ovalis | GB, VC17 Surrey, Weybridge | John Thomas Irvine Boswell-Syme | Frederick Janson Hanbury John Thomas Irvine Boswell-Syme | 8/1857 | BM |
| Carex otrubae x remota = C. x pseudoaxillaris | GB, VC17 Surrey, Wimbledon Common | John Thomas Irvine Boswell-Syme | John Thomas Irvine Boswell-Syme | 6/1857 | BM |
| Typha angustifolia | GB, VC17 Surrey, Wimbledon Common | John Thomas Irvine Boswell-Syme | Charles Ottley Groom | 1853 | BON |
| Carex paniculata | GB, VC17 Surrey, Woking,Basingstoke Canal | Hewett Cottrell Watson | John Thomas Irvine Boswell-Syme | 8/1870 | BM |
| Lathyrus aphaca | GB, VC18 South Essex, Leigh | John Thomas Irvine Boswell-Syme | | 9/1860 | BON |
| Spartina maritima | GB, VC18 South Essex, Leigh | John Thomas Irvine Boswell-Syme | | 8/1862 | BON |
+ | Lathyrus aphaca | GB, VC18 South Essex, Leigh on Sea | John Thomas Irvine Boswell-Syme | Charles Bailey John Ray Hardy | 8/1850 | MANCH |
| Elytrigia atherica | GB, VC18 South Essex, Southend | John Thomas Irvine Boswell-Syme | | 10/1865 | BON |
| Populus alba x tremula = P. x canescens | GB, VC18 South Essex, Wanstead | John Thomas Irvine Boswell-Syme | Donor Unknown John Thomas Irvine Boswell-Syme | 1853 | BIRM |
| Schoenoplectus lacustris | GB, VC18 South Essex, Woodford Bridge | John Thomas Irvine Boswell-Syme | Botanical Society of London Mantua And Montferrat John Thomas Irvine Boswell-Syme | 6/1853 | BON |
| Lepidium latifolium | GB, VC19 North Essex, Braintree | John Thomas Irvine Boswell-Syme | Augustin Ley | 4/1867 | BIRM |
| Lathyrus tuberosus | GB, VC19 North Essex, Fyfield | John Thomas Irvine Boswell-Syme | | 9/1860 | BON |
| Carex vulpina | GB, VC19 North Essex, Great Waltham | John Thomas Irvine Boswell-Syme | John Thomas Irvine Boswell-Syme Frederick Janson Hanbury | 5/1866 | BM |
| Carex otrubae x remota = C. x pseudoaxillaris | GB, VC19 North Essex, Halstead | Thomas Bentall | John Thomas Irvine Boswell-Syme Thomas Bentall | 7/1847 | BM |
| Peucedanum officinale | GB, VC19 North Essex, Kirby le Soken | John Thomas Irvine Boswell-Syme | Augustin Ley | 9/1867 | BIRM |
| Ruppia maritima | GB, VC19 North Essex, Kirby le Soken | John Thomas Irvine Boswell-Syme | | 9/1867 | BON |
| Bupleurum tenuissimum | GB, VC19 North Essex, Walton on the Naze | John Thomas Irvine Boswell-Syme | Augustin Ley | 9/1867 | BIRM |
| Carex vulpina | GB, VC19 North Essex, Walton on the Naze | John Thomas Irvine Boswell-Syme | John Thomas Irvine Boswell-Syme Frederick Janson Hanbury | 8/1867 | BM |
| Chenopodium glaucum | GB, VC19 North Essex, Walton on the Naze | John Thomas Irvine Boswell-Syme | London Natural History Society | 9/1867 | SLBI |
| Inula crithmoides | GB, VC19 North Essex, Walton on the Naze | John Thomas Irvine Boswell-Syme | William Hadden Beeby | 8/1867 | SLBI |
| Ruppia maritima | GB, VC19 North Essex, Walton-on-the-Naze | John Thomas Irvine Boswell-Syme | | 9/1867 | BON |
| Lepidium latifolium | GB, VC19 North Essex, Wivenhoe | John Thomas Irvine Boswell-Syme | Frederick Townsend | 9/1867 | SLBI |
| Carex paniculata x remota = C. x boenninghauseniana | GB, VC20 Hertfordshire, Hertford | William Higgins Coleman | John Thomas Irvine Boswell-Syme | 15/6/1842 | BM |
| Carex paniculata | GB, VC20 Hertfordshire, Ware | | John Thomas Irvine Boswell-Syme Frederick Janson Hanbury | 8/5/1847 | BM |
| Chenopodium chenopodioides | GB, VC21 Middlesex | John Thomas Irvine Boswell-Syme | Augustin Ley | 1851 | BIRM |
| Chenopodium polyspermum | GB, VC21 Middlesex | John Thomas Irvine Boswell-Syme | Augustin Ley | 1867 | BIRM |
+ | Chenopodium glaucum | GB, VC21 Middlesex, Belsize Park | John Thomas Irvine Boswell-Syme | Charles Bailey Hewett Cottrell Watson | | MANCH |
+ | Chenopodium glaucum | GB, VC21 Middlesex, Belsize Park | John Thomas Irvine Boswell-Syme | Charles Bailey | 9/1867 | MANCH |
| Potentilla reptans | GB, VC21 Middlesex, Belsize Park | John Thomas Irvine Boswell-Syme | Augustin Ley | 8/1867 | BIRM |
| Bromus secalinus | GB, VC21 Middlesex, Brentford | John Thomas Irvine Boswell-Syme | | 6/1867 | BON |