+ | Limonium binervosum subsp. sarniensis | GB, VC113 Channel Islands, Guernsey | William Williamson Newbould | Charles Bailey | 8/1841 | MANCH |
| Limonium humile | GB, VC13 West Sussex, Chichester | | Frederick Townsend William Williamson Newbould | 7/1843 | SLBI |
| Limonium vulgare | GB, VC113 Channel Islands, Saint Sampson's, Guernsey | William Williamson Newbould | | 1/9/1835 | SLBI |
+ | Linnaea borealis | GB, VC90 Angus, Clova,Glen Doll | | Isaac Bayley Balfour William Williamson Newbould | 1857 | MANCH |
| Lotus subbiflorus | GB, VC113 Channel Islands, Guernsey, Saint Martin's | William Williamson Newbould | Frederick Townsend | 8/1841 | SLBI |
| Ludwigia palustris | GB, VC113 Channel Islands, Jersey, Saint Peters | William Williamson Newbould | Allan Octavian Hume Frederick Townsend | 1846 | SLBI |
+ | Lychnis alpina | GB, VC90 Angus, Little Kilrannoch [Little Gilrannoch] | James MacNab William Williamson Newbould | Charles Bailey James MacNab John Harbord Lewis | 7/1832 | MANCH |
+ | Lychnis viscaria | GB, VC83 Midlothian, Edinburgh,Arthur's Seat | William Williamson Newbould | Charles Bailey John Ray Hardy William Williamson Newbould | 5/1850 | MANCH |
+ | Lychnis viscaria | GB, VC89 East Perthshire, Den of Balthayock | William Williamson Newbould | John Ray Hardy | 7/1849 | MANCH |
| Lythrum hyssopifolia | GB, VC113 Channel Islands, Jersey, Saint Catherine's Bay | William Williamson Newbould | Allan Octavian Hume Frederick Townsend | 8/7/1842 | SLBI |
| Matricaria recutita | GB | William Williamson Newbould | Frederick Townsend | 10/8/1852 | SLBI |
+ | Medicago minima | GB, VC15 East Kent, Ramsgate,Pegwell Bay | William Williamson Newbould | Charles Bailey John Hardy | 7/1843 | MANCH |
| Medicago sativa subsp. falcata | GB, VC26 West Suffolk, Thetford | William Williamson Newbould | Frederick Townsend | 15/8/1851 | SLBI |
| Mentha aquatica x spicata = M. x piperita | GB, VC29 Cambridgeshire, Barrington | William Williamson Newbould | | 9/9/1856 | CGE |
+ | Mentha pulegium | GB, Hampshire, River Erith | William Williamson Newbould | John Ray Hardy Susannah Mary Payne | 1841 | MANCH |
| Mentha pulegium | GB, VC31 Huntingdonshire, Earith | William Williamson Newbould | Frederick Townsend | 9/1884 | SLBI |
| Myrrhis odorata | GB, VC57 Derbyshire, Hathersage | William Williamson Newbould | Allan Octavian Hume Frederick Townsend | 7/11/1846 | SLBI |
+ | Neottia nidus-avis | GB, VC13 West Sussex, Goodwood | William Williamson Newbould | John Ray Hardy | 6/1843 | MANCH |
| Orchis mascula | GB, VC31 Huntingdonshire, Holme Fen | William Williamson Newbould | Charles Bailey John Hardy | 1846 | MANCH |
| Oxalis corniculata | GB, VC113 Channel Islands, Jersey, Saint Peters | William Williamson Newbould | Allan Octavian Hume Frederick Townsend | 18/8/1842 | SLBI |
+ | Oxytropis campestris | GB, VC90 Angus, Clova,Glen Doll | | Charles Bailey William Williamson Newbould | 8/9/1830 | MANCH |
| Persicaria mitis | GB, VC31 Huntingdonshire, Bluntisham | William Williamson Newbould | Frederick Townsend | 1845 | SLBI |
| Petroselinum segetum | GB, VC31 Huntingdonshire, Bluntisham | William Williamson Newbould | Allan Octavian Hume Frederick Townsend | 9/1845 | SLBI |
| Petroselinum segetum | GB, VC31 Huntingdonshire, Bluntisham | William Williamson Newbould | Frederick Townsend | 9/1845 | SLBI |
| Peucedanum palustre | GB, VC31 Huntingdonshire, Holme | William Williamson Newbould | Allan Octavian Hume | 16/9/1845 | SLBI |
+ | Peucedanum palustre | GB, VC31 Huntingdonshire, Holme Fen | William Williamson Newbould | Charles Bailey I Hardy John Ray Hardy | 16/9/1845 | MANCH |
| Polygonum aviculare | GB, VC17 Surrey, Norwood | Frederick Townsend William Williamson Newbould | Allan Octavian Hume | 27/8/1864 | SLBI |
| Polygonum oxyspermum | GB, VC113 Channel Islands, Guernsey | William Williamson Newbould | Frederick Townsend | 1841 | SLBI |
| Potamogeton coloratus | GB, VC29 Cambridgeshire, Bottisham Fen | William Williamson Newbould | Allan Octavian Hume Frederick Townsend | 23/7/1847 | SLBI |
| Potamogeton gramineus | GB, VC29 Cambridgeshire, Wicken Fen | William Williamson Newbould | Allan Octavian Hume Frederick Townsend | 8/5/1851 | SLBI |
| Potamogeton natans | GB, VC49 Caernarvonshire, Cwmffynnon | William Williamson Newbould | Frederick Townsend | 19/8/1847 | SLBI |
| Potamogeton pectinatus | GB, VC31 Huntingdonshire, Bluntisham | William Williamson Newbould | Charles Bailey John Hardy | 23/6/1846 | MANCH |
| Potamogeton pectinatus | GB, VC31 Huntingdonshire, Bluntisham | William Williamson Newbould | Frederick Townsend | 23/6/1846 | SLBI |
| Potamogeton polygonifolius | GB, VC13 West Sussex, Chichester | William Williamson Newbould | John Hardy | 10/1843 | MANCH |
| Potamogeton polygonifolius | GB, VC29 Cambridgeshire, Bottisham Fen | William Williamson Newbould | William Williamson Newbould | 23/7/1847 | SLBI |
| Potamogeton polygonifolius | GB, VC31 Huntingdonshire, Bluntisham | William Williamson Newbould | Charles Bailey John Hardy | 23/6/1846 | MANCH |
| Potamogeton polygonifolius | GB, VC63 South-west Yorkshire, Longley | William Williamson Newbould | John Ray Hardy | 7/6/1846 | MANCH |
| Potamogeton polygonifolius | GB, VC63 South-west Yorkshire, Loxley | William Williamson Newbould | William Hadden Beeby | 7/6/1846 | SLBI |
| Potamogeton polygonifolius | GB, VC63 South-west Yorkshire, Sheffield | William Williamson Newbould | Charles Bailey William Williamson Newbould | | MANCH |
| Puccinellia distans | GB, VC13 West Sussex, Chichester | William Williamson Newbould | William Hillhouse | 1842 | BIRM |