| Carex chordorrhiza | GB, VC77,VC78,VC83, Pentland Hills | Nicholas Tyacke | John Thomas Irvine Boswell-Syme William Williamson Newbould | 1843 | BM |
| Carex diandra | GB, VC90 Angus, Rescobie | Andrew Kerr | Botanical Society of Edinburgh William Williamson Newbould | 7/1841 | BM |
| Carex divisa | GB, VC25 East Suffolk, Walton | William Williamson Newbould | William Williamson Newbould | 8/1864 | BM |
| Carex divisa | GB, VC10 Isle of Wight, Gurnard Bay | Frederick Townsend | Frederick Townsend William Williamson Newbould | 6/1844 | BM |
| Carex divisa | GB, VC27 East Norfolk, Yarmouth | William Williamson Newbould | | 7/7/1847 | BM |
| Carex echinata | GB, VC5 South Somerset, Dunkery Hill | William Williamson Newbould | | 7/2/1850 | BM |
| Carex flacca | GB, VC13 West Sussex, Mundham | William Williamson Newbould | | 1843 | E |
| Carex lasiocarpa | GB, VC29 Cambridgeshire, Wicken Fen | William Williamson Newbould | | 15/7/1851 | BM |
| Carex lasiocarpa | GB, VC108 West Sutherland, Glen Canish | | John Thomas Irvine Boswell-Syme Nicholas Tyacke William Williamson Newbould Frederick Janson Hanbury | | BM |
| Carex leporina | GB, VC63 South-west Yorkshire, Aldwarke | | John Thomas Irvine Boswell-Syme William Williamson Newbould | | BM |
| Carex maritima | GB, VC108 West Sutherland, Polin | | William Williamson Newbould | | BM |
| Carex muricata subsp. pairae | GB, VC5 South Somerset, Dunster | William Williamson Newbould | | 25/6/1850 | BM |
| Carex otrubae x remota = C. x pseudoaxillaris | GB, VC19 North Essex, Inworth | Ezekiel George Varenne | William Williamson Newbould | 7/1847 | BM |
| Carex otrubae x remota = C. x pseudoaxillaris | GB, VC20 Hertfordshire, Buntingford | William Williamson Newbould | | 21/7/1848 | BM |
| Carex otrubae x remota = C. x pseudoaxillaris | GB, VC20 Hertfordshire, Layston | William Williamson Newbould | | | BM |
| Carex paniculata | GB, VC21 Middlesex, Willesden | William Williamson Newbould | John Thomas Irvine Boswell-Syme | 7/1867 | BM |
| Carex paniculata | GB, VC25 East Suffolk, Belton Fen | William Williamson Newbould | | 8/6/1847 | BM |
| Carex pseudocyperus | GB, VC15 East Kent, Sandwich | William Williamson Newbould | John Thomas Irvine Boswell-Syme Frederick Janson Hanbury | 20/7/1843 | BM |
| Carex remota | GB, VC20 Hertfordshire, Buntingford | William Williamson Newbould | William Williamson Newbould | 3/8/1847 | BM |
| Carex remota x vulpina = C. axilaris | GB, VC20 Hertfordshire, Buntingford | William Williamson Newbould | Allan Octavian Hume Frederick Townsend | 21/7/1848 | SLBI |
| Carex riparia | GB, VC31 Huntingdonshire, Somersham | William Williamson Newbould | Frederick Janson Hanbury John Thomas Irvine Boswell-Syme | 6/1846 | BM |
| Carex riparia | GB, VC21 Middlesex, Willesden | William Williamson Newbould | John Thomas Irvine Boswell-Syme | 7/1867 | BM |
| Carex spicata | GB, VC29 Cambridgeshire, Thriplow | William Williamson Newbould | Frederick Janson Hanbury John Thomas Irvine Boswell-Syme | 28/5/1847 | BM |
| Carex vulpina | GB, VC13 West Sussex, Chichester | | John Thomas Irvine Boswell-Syme William Williamson Newbould | 6/1843 | BM |
| Caucalis platycarpos | GB, VC29 Cambridgeshire, Harston | William Williamson Newbould | Allan Octavian Hume Frederick Townsend | 17/7/1848 | SLBI |
| Centaurea nigra | GB, VC61,VC62,VC64, York | William Williamson Newbould | Frederick Townsend William Williamson Newbould | 1/7/1846 | SLBI |
| Cephalanthera longifolia | GB, VC13 West Sussex, Goodwood | William Williamson Newbould | Allan Octavian Hume Frederick Townsend William Williamson Newbould | 6/10/1843 | SLBI |
| Cephalanthera longifolia | GB, VC13 West Sussex, Goodwood | William Williamson Newbould | | 6/1843 | SLBI |
| Cerastium fontanum subsp. vulgare | GB, VC29 Cambridgeshire, Gamlingay | William Williamson Newbould | Allan Octavian Hume Frederick Townsend | 5/4/1849 | SLBI |
| Cirsium heterophyllum | GB, VC57 Derbyshire, Hathersage | William Williamson Newbould | Frederick Townsend | 1846 | SLBI |
| Crepis foetida | GB, VC26 West Suffolk, Brandon | William Williamson Newbould | Frederick Townsend | 4/7/1848 | SLBI |
| Cuscuta epithymum | GB, VC29 Cambridgeshire, Whittlesford | Parnell William Williamson Newbould | Frederick Townsend | | SLBI |
| Cuscuta europaea | GB, VC29 Cambridgeshire, Waterford | William Williamson Newbould | Allan Octavian Hume Frederick Townsend | | SLBI |
| Dianthus armeria | GB, VC13 West Sussex, Chichester | William Williamson Newbould | Allan Octavian Hume Frederick Townsend | 10/1843 | SLBI |
| Dipsacus fullonum | GB, VC31 Huntingdonshire, Colne | William Williamson Newbould | Frederick Townsend | 1845 | SLBI |
| Dipsacus fullonum | GB, VC13 West Sussex, Chichester | William Williamson Newbould | Allan Octavian Hume Frederick Townsend | 1843 | SLBI |
| Epipactis phyllanthes | GB, VC20 Hertfordshire, Buntingford, Throcking | William Williamson Newbould | Frederick Townsend | 8/4/1847 | SLBI |
| Erica mackaiana | IE, VCH16 West Galway, Roundstone | William Williamson Newbould | | 5/1880 | SLBI |
| Eriophorum latifolium | GB, VC97 West Inverness-shire, Arisaig | Nicholas Tyacke William Williamson Newbould | Frederick Townsend | | SLBI |
+ | Euphorbia exserta | GB, VC13 West Sussex, Chichester | William Williamson Newbould | John Hardy | 10/1843 | MANCH |