| Vicia parviflora | GB, VC13 West Sussex, Heyshott | Iolo Aneurin Williams | | 7/1924 | SLBI |
| Senecio viscosus | GB, VC21 Middlesex, Chelsea | Iolo Aneurin Williams | | 5/8/1924 | SLBI |
| Sisymbrium pannonicum | GB, VC17 Surrey, Thursley | Iolo Aneurin Williams | | 9/1924 | SLBI |
| Potamogeton polygonifolius | GB, VC17 Surrey, Thursley | Iolo Aneurin Williams | Watson Botanical Exchange Club | 11/1924 | SLBI |
| Potamogeton polygonifolius | GB, VC17 Surrey, Thursley | Iolo Aneurin Williams | Watson Botanical Exchange Club Harold Stuart Thompson | 11/1924 | BIRM |
| Salix fragilis x triandra = S. x alopecuroides | GB, VC17 Surrey, Haslemere | Iolo Aneurin Williams | Watson Botanical Exchange Club | 23/5/1925 | SLBI |
| Carex echinata | GB, VC13 West Sussex, Redford | Iolo Aneurin Williams | | 19/6/1925 | BM |
| Carex ovalis | GB, VC17 Surrey, Milford | Iolo Aneurin Williams | Charles Edgar Salmon | 22/6/1925 | BM |
| Symphytum officinale x asperum = S. x uplandicum | GB, VC17 Surrey, Haslemere | Iolo Aneurin Williams | Watson Botanical Exchange Club | 24/6/1925 | SLBI |
| Potamogeton polygonifolius | GB, VC17 Surrey, Thursley | Iolo Aneurin Williams | Watson Botanical Exchange Club | 27/6/1925 | SLBI |
| Potamogeton polygonifolius | GB, VC17 Surrey, Thursley | Iolo Aneurin Williams | Watson Botanical Exchange Club Harold Stuart Thompson | 27/6/1925 | BIRM |
| Carex hirta | GB, VC17 Surrey, Frensham | Iolo Aneurin Williams | | 7/1925 | BM |
| Carex hirta | GB, VC17 Surrey, Witley | Iolo Aneurin Williams | | 7/1925 | BM |
| Ceratocapnos claviculata | GB, VC13 West Sussex | Iolo Aneurin Williams | Watson Botanical Exchange Club | 23/7/1925 | SLBI |
| Carex disticha | GB, VC17 Surrey, Thursley Common | Iolo Aneurin Williams | Watson Botanical Exchange Club Charles Edgar Salmon | 27/7/1925 | BM |
| Euphrasia anglica | GB, VC17 Surrey, Shalford Common | Iolo Aneurin Williams | Watson Botanical Exchange Club | 22/8/1925 | SLBI |
| Leontodon autumnalis | GB, VC1 West Cornwall, Ruan Pool | Iolo Aneurin Williams | Watson Botanical Exchange Club | 2/9/1925 | SLBI |
| Carex remota x vulpina = C. axilaris | GB, VC19 North Essex, Norton Heath | Iolo Aneurin Williams | Watson Botanical Exchange Club | 12/9/1925 | SLBI |
| Ranunculus omiophyllus x peltatus = R. x hiltonii | GB, VC14 East Sussex, Copthorne | Iolo Aneurin Williams | Watson Botanical Exchange Club | 27/3/1926 | SLBI |
+ | Ranunculus omiophyllus x peltatus = R. x hiltonii | GB, VC14 East Sussex, Copthorne | Iolo Aneurin Williams | | 27/3/1926 | BIRM |
| Mercurialis perennis | GB, VC17 Surrey, Thursley | Iolo Aneurin Williams | Watson Botanical Exchange Club | 22/4/1926 | SLBI |
| Carex acuta | GB, VC19 North Essex, Fyfield | Iolo Aneurin Williams | | 15/6/1926 | SLBI |
| Trifolium arvense | GB, VC29 Cambridgeshire, Furze Hills | Iolo Aneurin Williams | Watson Botanical Exchange Club | 8/7/1926 | SLBI |
| Euphrasia anglica | GB, VC18 South Essex, Blackmore | Iolo Aneurin Williams | Job Edward Lousley | 11/7/1926 | SLBI |
| Inula crithmoides | GB, VC11 South Hampshire, Hayling Island | Iolo Aneurin Williams | Watson Botanical Exchange Club Job Edward Lousley | 26/8/1926 | SLBI |
| Euphrasia micrantha | GB, VC23 Oxfordshire, Chinnor | Iolo Aneurin Williams | Watson Botanical Exchange Club | 11/9/1926 | SLBI |
| Chenopodium rubrum | GB, VC17 Surrey, Peasmarsh | Iolo Aneurin Williams | Watson Botanical Exchange Club Job Edward Lousley | 18/9/1926 | SLBI |
| Chenopodium rubrum | GB, VC17 Surrey, Peasmarsh | Iolo Aneurin Williams | Watson Botanical Exchange Club | 18/9/1926 | SLBI |
| Ranunculus peltatus | GB, VC17 Surrey, Chiddingfold | Iolo Aneurin Williams | Watson Botanical Exchange Club | 28/5/1927 | SLBI |
| Ranunculus peltatus | GB, VC17 Surrey, Ramsnest | Iolo Aneurin Williams | Watson Botanical Exchange Club Iolo Aneurin Williams William Harold Pearsall | 28/5/1927 | SLBI |
| Ranunculus peltatus | GB, VC17 Surrey, Ramsnest | Iolo Aneurin Williams | | 28/5/1927 | SLBI |
| Ranunculus peltatus | GB, VC17 Surrey, Ramsnest | Iolo Aneurin Williams | Watson Botanical Exchange Club Harold Stuart Thompson | 28/5/1927 | BIRM |
| Sisymbrium officinale | GB, VC24 Buckinghamshire, Slough | Iolo Aneurin Williams | Botanical Exchange Club of The British Isles Job Edward Lousley | 23/7/1927 | SLBI |
| Medicago polymorpha | GB, VC3 South Devon, Dawlish | Iolo Aneurin Williams | Botanical Exchange Club of The British Isles | 1/9/1927 | SLBI |
| Medicago polymorpha | GB, VC3 South Devon, Dawlish Warren | Iolo Aneurin Williams | Botanical Exchange Club of The British Isles | 15/9/1927 | SLBI |
| Medicago sativa subsp. falcata | GB, VC24 Buckinghamshire, Slough | Iolo Aneurin Williams | Botanical Exchange Club of The British Isles Job Edward Lousley | 1/10/1927 | SLBI |
| Chenopodium ficifolium | GB, VC24 Buckinghamshire, Iver | Iolo Aneurin Williams | Botanical Exchange Club of The British Isles Job Edward Lousley | 22/10/1927 | SLBI |
| Ilex aquifolium | GB, VC20 Hertfordshire, Berkhampstead | Iolo Aneurin Williams | Watson Botanical Exchange Club | 25/2/1928 | SLBI |
| Sagina boydii subsp. apetala | GB, VC113 Channel Islands, Guernsey, Cobo Bay | Iolo Aneurin Williams | Botanical Exchange Club of The British Isles Harold Stuart Thompson | 8/6/1928 | BIRM |
| Carex muricata | GB, VC113 Channel Islands, Guernsey | Alfred James Wilmott Iolo Aneurin Williams | | 9/6/1928 | BM |